292 Questions

[May70]

If I am still having an issues when I get everything back together I may consider replacing the filter sock. At least the sending unit is easy to get too. Only thing that would make it easier if my seat would fold over

When I shake my sending unit float I can hear gas inside. I put it in a bucket and it would float but not sure if it would hold up the arm. I went through the forums and read that one year Jeep sending unit float fits the factory Chevy truck sending unit. I actually found out its many Jeep models (1941-1986 MB, GPW, CJ2A, CJ3A, CJ3B, CJ5, M38, M38A1, CJ7, CJ8) Advance Auto had one under a 1986 cj7 that will be here for $12 shipped to the store. Its made by Omix-Ada, Float Fuel Sender part #17729.01 (they couldn't look it up under the number, only could find it under vehicle info). All plastic. It'll be here on Monday.

I mentioned before my fuel gauge has never worked for me. I went out to checked the sending unit was reading the correct resistance when the arm was manipulated and it was. In doing that I realized that the sending unit wasn't grounded with a separate wire like I saw some pictures of here. I am not sure if it needs a ground wire from the actual top of the sender unit for the stock tank. I figured it would have grounded through the tank bolting to the cab, I guess not. Simple enough fix, I dont have a male end or anything to connect a wire to so I may put a hole through one of the tabs or solder on a male connector of sorts. At least thats what I am hoping is the problem, the circuit diagram calls for the sending unit to be grounded. Diagnostic thread by VetteVet http://67-72chevytrucks.com/vboard/s...d.php?t=640615

Ill probably put the tank in Wednesday. Got in the new filler neck gasket from Wes at classic heartbeat, this one is very good quality and plenty of flex. Once the plastic float comes in I should be good to go come Monday. A place across the river from me sells non ethanol gas. I think my plan will be to run that in the truck from now out.

[Mike_The_Grad]

X2 on RichardJ post.
That sock is fine. Well it looks like you got your bases covered as far as the fuel system goes. Check for pinhole leaks in the metal fuel lines under the cab. Also, replace what ever sections of rubber fuel line you have from the tank all the way to the carb. Your sending unit will get its ground once the tank is mounted. Through the retaining bolts and the big flat square retainers that the bolts go through. Might as well replace your fuel pump while your at it. Unless it is already new. The rubber diaphragm inside can and will rot with age. I had to do all of these things when I got my 72 back on the road after sitting for 8 years in the driveway. Pulled tank, cleaned it, replaced sending unit, all rubber sections of hose, one of my metal fuel lines had a few pinholes in it, new fuel pump, had the carb rebuilt by a local carb shop, when I got it back the guy who worked on it asked me" What the hell did you do to this carb?" Lol. It was nasty inside. But when i got it back it was good to go. After all that, no more fuel problems, except the carb over the years since then.
That part number for the plastic float is the correct one. That's the one I put into my tank, couldn't be happier knowing I wont have to worry about the float leaking anytime soon. The other thing is my 72 has a EEC fuel tank. Which stands for Evaporation Emissions Control. It's got some internal tubes that are connected to a charcoal canister up in the engine bay, also a fuel pump with a return line, and a special type of gas cap. I cant recall off the top of my head what makes it so special. Mostly because I changed my fuel system different from stock. I no longer have the charcoal canister, my tank vents to atmosphere, so I also dont need a special cap. I still have the return type of fuel pump. I think the EEC setup is strictly for 72 trucks especially in california. The reason I bring it up is to male sure you have the correct gas cap for your truck and make sure no one has screwed with the fuel system like I have mine. Because these things will effect the performance of the vehicle.

[May70]

All that and the only thing that seems to have gone right is the gas gauge is moving around now. Well I am glad that I found out the situation I had in the tank and fixed that but, this is getting real old.

Absolutely no difference other than that. I cant even get it out of second (1st is granny) without it sputtering out. Give it gas up about 5 mph max try to go any more and sputters down, let off gas and it resumes idle. I guess its a carb issue still and im about ready to throw this monojet down the hill. I rechecked timing (just for sng), reset carb adjustments and redialed those in per instructions. Just tried to take it around the block and thought it was going to have me walk home.

[Seanext]

Ok, I just skimmed through the tread, just my two cents worth I didn't see anything on these items so if they are there please forgive me.

1. Vacuum advance take the distributor cap off then take the vacuum line and apply a vacuum source and make sure the advance is working as it should. Had a advance stuck on a V8 and had the same symptoms.

2. Take the gas line off the carb and place it in a gas can and spin the engine over and make you sure you have a good steady stream. I have seen a worn cam lobe for the fuel pump causing the engine to loose power when throttle is applied or could be bad fuel pump. This engine would run fine at idle.

3. Change coil I have seen coils break down as RPM's increase, run at idle but can't handle the rapid firing.

4. Fuel tank go to the pet store and buy the rough gravel that goes in a fish aquarium I used about 15lb fairly cheap but is small and will get in all the small places. I put in the back of my daily driver laying down and drove it for a couple days about 20 miles to work each way on one side then flipped it over and couple more days. Was clean as a whistle in just a few days. Yes it was a pain the rear to get all the gravel out but it is heavy and any that is left will fall to the bottom and stay. Ran that truck for several years with no issues and no chemicals to deal with.

Again if already tried sorry for wasting your time, just what I have seen over the years that may be causing you problems.

[Mike_The_Grad]

Well based off your vacuum readings and idle speed you have a healthy vacuum leak free setup. AT IDLE. But any other throttle position seems to cause problems. Have you tried leaving the vacuum gauge connected and manually working the throttle with your hand while it's in neutral? Like taking it up to 1,000 RPMS or 1,500 RPMS?

Can you post a few pics of your engine bay? Maybe theres something your not seeing that may be obvious to someone else. I know that this can possibly lead to "opening a can of worms" as some people may start questioning your setup. And that can spin off into another direction. But I think those of us who have been following this thread are just as curious as to why your truck ain't running right and want to help you figure it out. And without actually being there and only your info to visualize what your working on. Pictures do a great job of showing more of the whole picture.
Personally I take tons of pictures before,during, and after I'm working on something. I didnt always, but wish I had. Helps remind me of those "oh, I'll remember where this goes or how this looks when I put it back together" Times that I forgot how it was before I started...lol.

[May70]

Originally Posted by Mike_The_Grad

Well based off your vacuum readings and idle speed you have a healthy vacuum leak free setup. AT IDLE. But any other throttle position seems to cause problems. Have you tried leaving the vacuum gauge connected and manually working the throttle with your hand while it's in neutral? Like taking it up to 1,000 RPMS or 1,500 RPMS?

Can you post a few pics of your engine bay? Maybe theres something your not seeing that may be obvious to someone else. I know that this can possibly lead to "opening a can of worms" as some people may start questioning your setup. And that can spin off into another direction. But I think those of us who have been following this thread are just as curious as to why your truck ain't running right and want to help you figure it out. And without actually being there and only your info to visualize what your working on. Pictures do a great job of showing more of the whole picture.
Personally I take tons of pictures before,during, and after I'm working on something. I didnt always, but wish I had. Helps remind me of those "oh, I'll remember where this goes or how this looks when I put it back together" Times that I forgot how it was before I started...lol.

I will try this and get some pics. First I am going to check my ignition coil when I get back, that I have not replaced. If the coil checks out I may throw the old condenser back on it just to see if that changes anything. Ive heard of people getting lemon distributor condensers from the parts store. As far as carb internals I dont see how I could have screwed that up, I took it apart and checked with the diagrams so many times. If it were an adjustment problem I would think the issue would change slightly as I messed with it and it hasn't.

Ive read a (going) bad coil can have same issues as mine. I mentioned the last time I was driving it longer distance it was surging/loosing power at 45ish mph and I had to limp it home. The problem has progresses to where it is now and I just assumed carb problems. Perhaps it is the coil/condenser. I am getting spark to the plugs at idle but at higher rpm/load im not sure.

I do feel like I am just grasping but hopefully with what I have done I am narrowing down the issue.

[Steeveedee]

Originally Posted by Seanext

Ok, I just skimmed through the tread, just my two cents worth I didn't see anything on these items so if they are there please forgive me.

1. Vacuum advance take the distributor cap off then take the vacuum line and apply a vacuum source and make sure the advance is working as it should. Had a advance stuck on a V8 and had the same symptoms.

2. Take the gas line off the carb and place it in a gas can and spin the engine over and make you sure you have a good steady stream. I have seen a worn cam lobe for the fuel pump causing the engine to loose power when throttle is applied or could be bad fuel pump. This engine would run fine at idle.

3. Change coil I have seen coils break down as RPM's increase, run at idle but can't handle the rapid firing.

4. Fuel tank go to the pet store and buy the rough gravel that goes in a fish aquarium I used about 15lb fairly cheap but is small and will get in all the small places. I put in the back of my daily driver laying down and drove it for a couple days about 20 miles to work each way on one side then flipped it over and couple more days. Was clean as a whistle in just a few days. Yes it was a pain the rear to get all the gravel out but it is heavy and any that is left will fall to the bottom and stay. Ran that truck for several years with no issues and no chemicals to deal with.

Again if already tried sorry for wasting your time, just what I have seen over the years that may be causing you problems.

A bit about #2- the off-idle stumble shouldn't be caused by low fuel flow, since the carburetor bowl would still be full, and we've seen that. It is entirely possible that the lobe has flattened over time, since it was running OK and the road speed performance deteriorated over time.

I'm still thinking ignition, though.

[May70]

I took a reading on the ignition coil: Primary was 1.8 and secondary resistance was 9860 ohms. Both are high according to the tune up chart. I honestly don't know enough to know if that is a problem. I let it idle for about 15 minutes and took it around the yard. With the engine temp warmed up the coil read 112F with my temp gun.

Out of the three multi-meters I have, non have a setting for microfarad so I cant test my distributor condenser that I know of. The tune up chart calls for . 18-.23 microfarad. I took out the new one and put in the old one and there is no difference. Truck stumbles out if you try and give it much gas at all as it did before.

I put it in neutral and plugged in the vac gauge. At idle its reading about 22 but as soon as I give it gas the vac drops quickly down to 0.

[Steeveedee]

Do you just barely crack the throttle, and vacuum goes to zero?

[May70]

I made a video. Me trying to explain it isnt going so well ha ha. I can tell you where it drops off is right at the high point of second gear and it refuses to get enough 'get up and go' to run in third gear. Maybe 5-10 max mph before it drops off like that. Its also not exactly the same behavior when you give it gas. To get the truck going into that 5-10 range you really have to feather it to keep it from stumbling earlier than that.

https://youtu.be/_XV4xJVREMg

[Steeveedee]

Alrighty then! Drop the head pipe off the exhaust manifold and try again. You may have a collapsed exhaust pipe or broken baffle in the muffler. It shouldn't go all the way to zero like that. Try it and let us know. I had a slagged converter on one of my cars and the vacuum didn't drop that fast. Yours isn't backfiring out the carb, so it's probably not a fuel problem. Also make sure that the heat riser valve is open.

[Mike_The_Grad]

Wow, that video helps for sure. Something is definitely amiss with your setup. Steeveedee is on to something. I've not seen a steady rise in intake vacuum as the throttle is opened like yours does. Then immediately drop to zero like that. Read up some more on vacuum gauge reading. There's something to explain the sudden drop like that. Also sounds like you got a knock or something that is rpm related. I could be wrong and just hearing things. Either way, I'd start at the exhaust manifold and work your way back to the end of the tail pipe. But the heat riser valve is probably gonna be the culprit. Do you have it connected properly? I couldn't tell you what it's supposed to look like or how it functions. Never had one and I just put headers on my dads 292. My guess is that its malfunctioning or inoperable. Especially because you say that youve let the engine warm up and it still reacts the same regardless.

[May70]

Originally Posted by Mike_The_Grad

Wow, that video helps for sure. Something is definitely amiss with your setup. Steeveedee is on to something. I've not seen a steady rise in intake vacuum as the throttle is opened like yours does. Then immediately drop to zero like that. Read up some more on vacuum gauge reading. There's something to explain the sudden drop like that. Also sounds like you got a knock or something that is rpm related. I could be wrong and just hearing things. Either way, I'd start at the exhaust manifold and work your way back to the end of the tail pipe. But the heat riser valve is probably gonna be the culprit. Do you have it connected properly? I couldn't tell you what it's supposed to look like or how it functions. Never had one and I just put headers on my dads 292. My guess is that its malfunctioning or inoperable. Especially because you say that youve let the engine warm up and it still reacts the same regardless.

Are you talking about this? Its got one of the heat release springs on it and its not stuck. The exhaust manifold I just bought a few months ago. With the engine about warm its still in the same place though. I held it open all the way (i guess) and gave it gas, no change.

I dropped the exhaust and cut off the muffler, then I put the pipe back on it just so I wouldn't get smoked out. Muffler looks fine inside. Definitely not the problem. I made another video just to show its the same exact thing. No difference that i see.

https://youtu.be/mRvxsyky7pg

That sound that was mentioned is definitely there. Not sure if thats considered a knock or what but when I first brought it home didnt notice it.

[Steeveedee]

OK, so I'm not clear on the process. Did you run it at all with the pipe disconnected from the exhaust manifold?

[May70]

Yes its off at the exhaust manifold right now and just did the same thing. I even put a scope through the straight pipe with it off, its clear.

[RichardJ]

Your previous question about the condition of the points condenser can be best answered visually. If metal is being transferred from one point contact to the other, the condenser value is incorrect. Don't confuse normal pitting wear with metal transfer. Normal pitting can be cleaned up with a small point file.

[May70]

Originally Posted by RichardJ

Your previous question about the condition of the points condenser can be best answered visually. If metal is being transferred from one point contact to the other, the condenser value is incorrect. Don't confuse normal pitting wear with metal transfer. Normal pitting can be cleaned up with a small point file.

The points are brand new. I gaped n new points so they shouldn't be rough like in the picture. My dwell is dead on 31. My post about wanting to test the condenser was just to make sure it was operating as it should. I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading (the only values I gave were for the ignition coil?). Im confused

[RichardJ]

>> My post about wanting to test the condenser was just to make sure it was operating as it should.<<

The condition of the point contacts will tell you if it is operating properly.

>> I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading <<

The condition of the point contacts will tell you if the condenser value is correct.

If you post again that you don't have a capacitance meter, I'll repost the same information in English next time.

If you tossed the old points, take a look at the new ones to see if anything is beginning to look abnormal.

I'll try one more thing. In lieu of a Capacitance Meter, the condition of the point contacts will tell you everything you need to know about condenser. End of story, move on.

On your video, were you connected to a vacuum port that you are positive has full manifold vacuum at all times?

Reconnect the dwell meter and the vacuum gauge and repeat your video test. You need to look and verify that the dwell stays consistent and steady at or near the 31* you reported.

[Steeveedee]

Thinking more about this, what do the wire running to the points and the breaker plate to ground wire look like? Check the ends especially to see if there are a bunch of broken filaments. It could be that there are enough for idle and a bit of speed, but not enough to carry current when the engine is under load. I don't think that this was mentioned before. The breaker plate ground wire flexes as the vacuum advance moves, so it can eventually wear out.

[May70]

Originally Posted by RichardJ

>> My post about wanting to test the condenser was just to make sure it was operating as it should.<<

The condition of the point contacts will tell you if it is operating properly.

>> I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading <<

The condition of the point contacts will tell you if the condenser value is correct.

If you post again that you don't have a capacitance meter, I'll repost the same information in English next time.

If you tossed the old points, take a look at the new ones to see if anything is beginning to look abnormal.

I'll try one more thing. In lieu of a Capacitance Meter, the condition of the point contacts will tell you everything you need to know about condenser. End of story, move on.

On your video, were you connected to a vacuum port that you are positive has full manifold vacuum at all times?

Reconnect the dwell meter and the vacuum gauge and repeat your video test. You need to look and verify that the dwell stays consistent and steady at or near the 31* you reported.

Thanks for clearing that up RichardJ, keep your patience with me!! I think ive mentioned, I have little to no experience in this stuff. Learning as I go. Unfortunately my family/friends who knew this stuff are dead, so I basically have this forum and google. I appreciate you spelling it out, I wasn't tracking that one.

I got the drift now of what you meant and will check those points you made out in the morning.

I am going to try and find a carb from a friend to swap on there and see if that changes anything. I am looking for something to change the symptoms and go from there.

Stevee Ill take a picture of my distributor internals in the AM. Thanks gents....

[Steeveedee]

Originally Posted by May70

Thanks for clearing that up RichardJ, keep your patience with me!! I think ive mentioned, I have little to no experience in this stuff. Learning as I go. Unfortunately my family/friends who knew this stuff are dead, so I basically have this forum and google. I appreciate you spelling it out, I wasn't tracking that one.

I got the drift now of what you meant and will check those points you made out in the morning.

I am going to try and find a carb from a friend to swap on there and see if that changes anything. I am looking for something to change the symptoms and go from there.

Stevee Ill take a picture of my distributor internals in the AM. Thanks gents....

I'm not sure that a picture will work, unless you have way better skills with a camera than I have (which wouldn't be all that much- my camera skills are pretty much non-existent). It's going to rely on you wiggling the wires to see if a lot of the strands are broken. This is just another check, and hopefully it's an answer. But not being in front of it, it's just hopeful that we finally guess a solution over the internet. By the time this is figured out, you'll be an ace on troubleshooting these old trucks. It's pretty much how we all learned it, back in the day. But we didn't have the internet then. Did you download the Factory Service Manual for your truck? Not that it would necessarily help, at this point. Those manuals discuss problems back when the vehicles were new, and didn't have corroded and/or worn wiring and serious age on them.

On the topic of checking the condenser, that takes a type of equipment called a "Decade Box", and isn't something that a mechanic would normally use in the repair business. In 25 years of working on vehicles, I never used one- it is for the electronics guys, and I'll bet if you went into a repair shop today, you'd never find one. The dwell-tachs don't have it for this reason.

"Fun" story about condensers- one of my friends put a bunch of Mallory tune-up parts in his '62 Corvette. A few days later, it rolled to a stop. He couldn't figure it out, did a valve job and all kinds of stuff. It still wouldn't start. In the process of pulling the distributor cap off and checking the points for about the 10th time (because there was no spark- the original problem, btw), he managed to pull the wire out of the condenser by accident! All that unnecessary expense and time for a failed condenser. We just looked at it like, WTH? a brand new part! He went on to be a really good mechanic, and did it for a living for 40+ years.

[May70]

The guy I talked to only has 4 barrels so that idea seems to be gone. Didnt get a chance to look at the truck today, bad weather here. Talked to another guy today and he was scratching his head on the subject and he did fleet maintenance back in the day on a lot of 292s.

[May70]

How about some inputs on this.... Maybe years of experience and what ive got here might light a bulb for someone.

I did some searching for more info on using vacuum to diagnose issues. Everything I have read only lists one reason for vac going to zero. But the vacuum shows some fluctuation before dropping toward zero which got me thinking.... I know the exhaust is not blocked so maybe that initial fluctuation means something...

Looking at the second video I posted ( Post #163) with the muffler off ( I got the same readings with exhaust off at the manifold); It holds a relatively steady 22 at idle. There is no fluctuation until accelerating, when it decreases to 20 then increases to 23 after that point it drops off to zero. I see two distinct patterns first a fluctuation off idle from 20-23, then with continued acceleration a drop off towards zero while noting the engine sounding like its dying off. With that in mind, I found this article out of a pop mechanic magazine which gives the best guide ive been able to find.

Looking at Case #5 in the picture from pop mechanics: Normal and steady reading at idle, but vibrating reading at high speed - weak valve springs. Does this explain the first pattern of fluctuation between 20-23?

I found another guide on another forum that indicated similar (second pic).

Could it be possible that an extreme case of the valve springs being weak cause essentially a complete loss of power/vac with acceleration? If the engine is dying out, wouldn't that cause the vac to go to zero as a result?

Also looking at #1 and #2 on the pop mechanic article, to me that is saying I do not have an issue with either my carb settings at idle or the wrong timing. Is that a leap too far?

[May70]

Richardj,

Aside from what I posted above, here is a follow up to your previous message and some others. I just went out to look at the distributor. The two wires looked ok, they weren't loose and I didn't see any frays. I checked to make sure I couldn't rotate the cap with the bolt tight, It didn't rotate. Then I took the cap off and turned the shaft and let go and it seemed to spring back to where it was. I then checked to see if I could move the plate with the vac advance attached, I couldn't. The points look ok to me, I put the new condenser back in it because the old points looked rough (pics of new and old points below).

When I started it up I noted the timing had advanced more than it was before. High rpm about 1200 and it sounded like it was missing. I thought that the springs would bring it back to the timing I had it at before. Maybe Ive got something confused.. anyway

I started to re adjust the timing, at around 0-2 degrees the vacuum reading was about 18 and the truck would die out much quicker than before. It seemed like the symptoms were intensified. I set it back to 12 degrees of advance and it followed the basically same pattern as in the videos previously at an idle vac reading of 22. Dwell was at 31 at idle but it would drop to 28/29 when I gave it gas. Idle rpm was roughly 580. As I changed the advance I would tweak the carb to keep the rpm under 600.

Im not sure if this info means something or if I can use it to narrow down anything. Since I had to tweak the carb with the advance changing im not sure I can say if the issue is ignition.

[Steeveedee]

Are you absolutely certain that the heat riser valve is open, hot? You can verify that by poking the counterweight with something, since it will be hot. I believe you replaced the exhaust manifold, so the heat riser valve is new? Didn't want to read through it all again, sorry.