Missing Issue / Possible Fuel Pump Failure

[Spline64]

Hey all,

Well, engine started randomly missing recently and after checking possible electrical issues first, discovered that the fuel filter had some large visible debris in it. Yeah, I know, don't use the plastic ones but it did show contamination so pointing me in the right direction.
Checked the fuel pump output and got about 1/3 of a cup in 5 seconds along with one small piece of debris that matched what was seen in the filter. I'm not sure if that flow is acceptable or not, but have noticed that sometimes the fuel doesn't always fill the filter.

So....I guess I have a couple of questions:

I have attached pictures of the debris. While the pics don't show it, the debris will float on gas and looks line a fine lint with jello qualities. How could this contamination come from the gas tank since it floats so well?
Is it possible that the diaphragm of the pump has failed and this is the debris I am seeing?
I've already purchased, for the massive sum of 24 dollars another filter and fuel pump and will be installing them tomorrow morning but was curious what you guys thought about the pics and if just maybe something corroded / failed in my gas tank (single tank system) or am I the victim of a random drunken angry person....
Don't want to filter my tank 24 bucks at a time.

Thanks,
Spline64

[franken]

I think if the pump diaphragm (is that spelled right?) had failed there would be gas in the oil.
Sadly, gas today has methanol which attracts water and is corrosive. If a vehicle sits, it will absorb moisture from the air, which over time will settle out of the fuel and rot whatever it gets in contact with. Like the gas tank, lines and carb. That's why I run small engines out of fuel at the end of the season.
Whatever it is, it pretty much has to come from the tank so drive it to move it through the system.
I'd guess a miss is from something else and this is just a side issue.

[Spline64]

Ok, been working on this missing issue for a while now and feel like I'm getting nowhere except losing weight as my wallet doesn't way as much as it did when this problem started.....

I have replaced the following:
Fuel Pump
Fuel Filter
Distributor Rotor and Cap
Plug Wires
Spark Plugs

Checked Timing (at 10 deg initial, has always liked this setting)

It certainly starts quicker now but still misses very badly, engine shaking at idle and low RPM's. In fact to even idle, I have to turn up the idle speed. Won't idle without it. Mixture screws are practically worthless. I also noticed that if I put my foot in it, I get a bogging hesitation before it takes off. It will start to go but then bogs down. Once above a certain RPM goes like crazy. Could this be a vacuum leak or maybe a carb problem? It has never bogged down before and really sounded like the secondaries opened. The electric choke is busted so replacing the carb is gonna happen eventually but would like to have some evidence before I plunk down $400
The engine has about 15,000 on it after a rebuild. I'll check compression as well but wouldn't think that this would be my issue since it takes off like a bat outta hell above a certain RPM, and sorry don't have a tach on this truck.
This problem happened slowly over a couple of weeks before it got so bad I didn't want to drive it anymore. Not sure if that is a sign of what might be going on or not.

Thanks,
Pat

[buddy_1]

Are you seeing any smoke at the tailpipe? If so what color? Sounds like it is flooding at idle. Look for black smoke when trying to accelerate

[Spline64]

Thanks buddy_1

No smoke at all, never has.... at least visible anyway.

For what it's worth, the exhaust smells "more sweet" than it used to.

Thanks again for the reply!
Pat

[lowbucktrucks]

sweet smell is often antifreeze could be blown head gasket or cracked head or block
time for a compression check

[buddy_1]

Another thing to check would be both vacuum and mechanical advance operation. Diaphram should hold vacuum and centrifical weights should move freely when moved by hand.

[Spline64]

Been awhile but still having issues......latest update

Have performed a vacuum test at intake manifold. Needle is all over the place between 15 and 25. Engine struggles so hard to idle you can actually hear the fuel in the carb throat "cut out" at times when it's trying to die.
Performed compression test (see attached). I do show a 11 psi difference between highest and lowest readings but need to know if that could actually cause what I have described.
No oil or coolant leakage at all, no cross contamination.
Looking at possible intake manifold leak now??

thanks for all the help so far,
Spline64

[MrDanB]

I had an Olds years ago that had this exact same problem. Turned out to be a condenser. If you have the old points style distributor, check that next as it would definitely give you a horrible "miss" while running... Good luck with it!

Dano

[Gregski]

Originally Posted by Spline64

...discovered that the fuel filter had some large visible debris in it. Yeah, I know, don't use the plastic ones...

Says who, I had all sorts of problems with those fancy more expensive glass ones, I went back to using the plastic one and problem solved, also less likely to shatter, just replace them more often

what year was your truck? does it have points or HEI distributor, if points you may want to upgrade to HEI for $150 and never look back, what about the coil, did you replace that? could be a cheap fix?

just trying to help

[Spline64]

Thanks guys!

The truck is a 1973 but the engine is not the original. Carb with HEI.
Have not yet changed its coil.
but this story just keeps getting weirder and weirder....

So after performing the compression check, put all plugs in and wires back on and all the sudden it has a high but smoother idle. Did another vacuum check and NOW it is fairly solid at 40 psi, only dropping when the engine stumbles. When cold I can swear I hear a slight whistle that goes away when heated up.
By the way the idle is high enough to start you from a dead stop without depressing the accelerator. The idle speed screw is out all the way and idle mixture screws are almost all the way in (1/2 turn from bottoming out). The idle does lower a bit after it gets hot, but becomes more choppy.
I had mentioned earlier in this post that I could hear the secondaries kick in, now the performance is decreased and I can no longer hear them.

So the obvious....I changed something by reinstalling the plugs and wires. But then why did it run well and get worse over 2 weeks time before any of this? Perhaps I made it easier for the voltage to travel to the plugs indicating the coil is going out? I'm having a hard time believing that a failing coil could make the idle higher.

I can see a vacuum leak causing this but can't understand how it can be "off" then "on"

Spline64

[Chaplain]

Whoa...wish I could help.

[Spline64]

So in looking for another source for my "vacuum leak" I used a pair of vise grips to pinch off the brake booster vacuum hose. Since my engine can barely idle, I decided to pinch it before I started the engine.
Cranked it about 3 revolutions and could actually see (quite a bit actually) gas vapour coming out of the air cleaner. Sounded very strange as well. Removing the air cleaner showed much more in the throat of the carb, almost like I had reversed the direction of air flow. Not going to repeat this obviously till I know what the heck happened.

Please someone out there tell me that I am doing something stupid cause I really don't see how this is possible.

Thanks,
Pat

[bmchevy1979]

Idk about the last post. But I have had a hei coil that had a similar signs but what went bad was the wire that feeds the tach signal it broke in the insulation just before the coil but it was more reactive when you hit a bump but would stumble from a start it finally went completely out and when I replaced coil the wire fell into my hand while I was matching it up to the new one

[Spline64]

That is actually interesting as I had issues with the battery connection to the distributor cap. I don't have a tach however. Had to solder a new wire connector over a year ago. Still seems to fit well and snug but I could see how with all the vibration it might not be as solid as it was before.
Again I don't understand how if you have a bad electrical connection, giving it more gas solves the problem. When I had the issue of the battery connection to the dist cap, it wouldn't even start (randomly by the way).
Thanks, gonna check this, hell who knows at this point.

Pat

[bmchevy1979]

Well the charging system on my truck works really well and even works better when you give it rpm so my theory was the increase in voltage was easier to jump the gap in the broken wire

[Spline64]

Sorry guys, I know this is an old thread but I have to try one last time.

current speculations --
A vacuum leak, rather large one. I have changed carb gaskets (again) to no avail. Sprayed around the intake and carb to see if I could hear change in idle, none detected but I can't reach to the back of the block behind the dizzy. Now that it is hotter here, engine has a pathetic idle at least to have accomplished this test.
Tested the brake booster with simple pumping the brakes with engine off, held, started engine and it depressed another inch and a half so should be fine right? Then why when I plug this line to the carb, I get backfires out of the carb upon acceleration (in park) like I've changed the whole flow schematic? It can only barely idle, scary actually.

Ran great for at least 6 months, started to show light symptoms of something was amis for 2 weeks that got worse and worse. It did get quite hot parking a trailer another month before that but never overheated. I have always considered this, but she never leaked antifreeze, no mix in oil. All parts listed below were not changed till after symptoms occurred:

I have replaced the following:
Fuel Pump
Fuel Filter
Distributor Rotor and Cap and Coil
Plug Wires
Spark Plugs

Checked Timing (at 10 deg initial, has always liked this setting)

Is there anything left like a module in the dizzy that can create these type of symptoms???

Before I pull the intake manifold.........

Thanks again!

[JohnnySpeed]

I chased something very similar to this for over a year. Turned out that it was the ceramic ring piece inside the distributor under the rotor. It had a crack in it. Very hard to see until the distributor was out. It cannot be replaced must replace entire distributor. Robbed one out a junk car and it ran great. I hope you figure it out.

[cadillac_al]

That backfirng and spitting gas out the carb sounds like a possible bad cam lobe. It may still have a bad vacuum leak too. It took me 2-3 weeks to find a vacuum leak on my Caddy. I usually disconnect all unnecessary vacuum lines, but I am trying to keep all 200 vacuum lines on the Cad.

[Spline64]

200 vacuum lines....sheesh.....I have 4 and can't find a damn leak
Going to pull the valve covers this weekend and look for a possible cam lobe issue. It only backfires when the brake booster vacuum line is plugged btw.

Distributor comment got me wondering. Mine tilts quite a bit but can't remember if it always looked like that or not and not sure if this could cause an issue. Might be totally normal, never had a 454 before. I attached a pic of it. No strange wear in the old or new cap, base is tilted too.

Thanks again

[Spline64]

Will this ever end.....??

Latest update:

I have replaced the following:
Fuel Pump
Fuel Filter
Brand New Distributor with another brand new Rotor and Cap and Coil
Plug Wires
Spark Plugs
Replaced Intake Manifold Gaskets (with Felpro Gaskets)

I will be taking the valve covers off tomorrow (just replaced the dizzy tonight) to look for a bad or several bad cam lobes.
There is however one thing that can make the engine run very smooth but have a high idle....close the choke. To me this is screaming "vacuum leak" but I have no idea where since I have checked or replaced every vacuum point I could find including intake manifold gaskets. Would a bad cam lobe or lobes act in this fashion?

While I did swap the carb with a used one and got the same symptoms, but a little better idle (600 cfm to 650 increase in carb size), I have to wonder, could it really be the carb? Damn thing sounds like it is randomly spitting into the intake even when you add the choke to get a smooth idle. You have a smooth "spray" sound then it "spits". Nothing comes out of the carb. That only happens when you plug the vacuum line to the brake booster.

I'll write back tomorrow with the results of the cam lobe test. ANY ideas would be appreciated.

Thanks

[77 Big 10]

Your compression numbers are fine and it sounds like a vacuum leak to me also. Is the line down to the trans vacuum modulator hooked up? You can block off all the vacuum ports and it will still run, maybe try that and see if it idles right. Pinching off the brake boost line should not make a difference, not sure what is happening there.

[geezer#99]

Interesting story!
Would be better with a nice pic or two of your motor!!

[77 Big 10]

I agree Geezer, it sure would be easier to spot a problem, if we had something to spot.

[Spline64]

Ok, pulled the valve covers and cranked with battery wire to distributor disconnected. Made a little movie, zipped it but 3mb is way over the 100k limit so can't show you. As far as pictures, I have to take these to work tomorrow to be able to compress down to even attach (really old camera).

I can't see any rocker acting differently, all seem to move the same distance. When I had the intake manifold off, checked all the rods, looked good, nothing bent. Put the valve covers back on but didn't tighten them down in case someone has something else to suggest in this arena.

So will send pics tomorrow, the little movie shows it best but I understand the file size limit. Had checked the vacuum line to the TH400 tranny before but I admit I didn't clean it as well as I should have. When running the engine for the first time I didn't have this hooked up (plugged) and wouldn't change gears. hooked it up and ran great for 6 months so didn't think it could be the issue but will check again.

Thanks,
Pat