Timing issues?

[bulkin'up73chevy]

Hi guys been a long time since i've posted on here the whole busy life thing keeps tying me up.

I finally pulled my 86 out of the shop to get her going again. And low and behold that mean dealing with the issues that hid her there in the first place.


Truck info.

1986 C20
second owner
california emissions.
350 rochester carb on top.
There is no ecu. just smog equipment.

The Problem

3 years ago the truck started missing/backfiring. throwing fire out the exhaust horribly. and up the top. I took the truck to a local shop seeing as i'm no expert just a usual diy.er. They first said the cam was bad. pulled it out inspected it, and it was fine. rebuilt the carb. Put a new timing chain on. adjusted timing. same problem.... called me a month later and told me to get it off there lot with no change. and stole my exhaust. Now getting back into her. Today I put fresh fuel, and oil. and she sounds alright but still the same as 3 years ago. any idea to the issue?

[old Rusty C10]

the distributor? or at least the module in it.. ive had issues with KEM brand modules where they have been bad right from the parts store

[terryj]

From the sound of your symptoms its a timing issue, simple things first, check your plug wires and make sure their going to the correct plugs, 1-8-4-3-6-5-7-2 in a clockwise direction on your distributor cap. Normally if it is the ignition module you'll get no spark at all, these are normally "run/no run" modules. Check inside your distributor for cracks, carbon tracks and loose wires. It sounds like your getting spark but not in the right firing order. Remember these are HEI systems so be carefull they knock you on your butt.

[Cue-Ball]

I'm with terryj. Definitely sounds like something wonky going on with the spark. Check all the easy/free/cheap to fix stuff first, then move on to other possibilities. If everything he suggested checks out, you could try a cheap junkyard distributor just to rule out problems with the magnetic pickup, wires, etc.

[bulkin'up73chevy]

Thanks guys I ran her today up to my logging lot and going uphill she just lost all power had to tow her home. Tomorrow morning I will be doing just as you said, although firing order is in all good shape I already checked that. I'll be going in this order.

Distributor inspection/ replacement parts.
Timing w/ timing light check the distributor isn't 180 out.
Plug wires and plugs.
Compression test.
Timing chain if no change after that.

There is no knocking and/or tapping at all internally so I'm sure all that checks out hopefully the shop didn't screw me over then and come to haunt me now.

i finally got the idle down today after getting her running. The never hooked up the vaccuum from the brake booster. "JUST SUCKING AIR IN"

Another question is about california emissions. any of you know where all these damn hoses go?

[terryj]

Do you still have the stock air cleaner? If so there should be vacuum routing on it. If you can find the 3 letter code which should be in the upper left hand corner of the sticker on the air cleaner housing, let me know the code and I can help you with the hose routing.

[Dan1969]

It's a firing issue as previously stated. Replace your coil, module, wires, sparks (properly gapped), cap and rotor, clean vaccuum advance and weights, and adjust timing. You can clean your Carbureator and replace vaccuum lines along with PCV Valve and fuel filter. That's just my two cents. It'll be about 100 bucks worth of parts and easily done in your driveway, given that's not raining.

[bulkin'up73chevy]

Originally Posted by terryj

Do you still have the stock air cleaner? If so there should be vacuum routing on it. If you can find the 3 letter code which should be in the upper left hand corner of the sticker on the air cleaner housing, let me know the code and I can help you with the hose routing.

Thank you. I do have the stock air cleaner i'll go pull those numbers off for you. I appreciate your help.

Originally Posted by Dan1969

It's a firing issue as previously stated. Replace your coil, module, wires, sparks (properly gapped), cap and rotor, clean vaccuum advance and weights, and adjust timing. You can clean your Carbureator and replace vaccuum lines along with PCV Valve and fuel filter. That's just my two cents. It'll be about 100 bucks worth of parts and easily done in your driveway, given that's not raining.

Thank you Dan1969 I have already checked timing today. Already has a brand new CAP, AND ROTOR. I have never cleaned a vaccuum advance. How do I go about doing that? and what are the weights you are referring to? I have never heard of those.

It appears as though there is an ICM under the cap that I have never seen in this series of truck "PRE-TBI" and there is no ECM to operate the ICM on the truck. I am tearing down the distributor as we speak.

I will be rebuilding the carburater tomorrow AGAIN! Making sure the floats aren't stuck or have rusted in the time it sat.

I will be taking pictures and posting within the hour.

[bulkin'up73chevy]

here are some pictures. Air cleaner code. "UKS"

both air pumps are in working order. vaccuum lines hooked up to the necessities. Transmission. vaccuum advance. others plugged temporarily.

Note: Everything was hooked up correctly when it started this problem three years ago. this is what I ended up with after getting it back from the shop. with the acception of the disassembled distributor. That I did.

[bulkin'up73chevy]

and here is the distributor. Still confused about "Weights"

[terryj]

I'll tell ya, if it were me, I'd be scraping most of that somg crap off the truck, I believe that in Washington and thing over 20 years old doesn't need IM'd. All that stuff does is drain the hp fromthe engine. The Rodchester Q-jet is a fuel hungry carb, most likely you were getting about 8-10 mpg. If you can get your self a set of headers and a different carb for that 350. I have the same truck, mine is a 83 C20 with the 350 vin M engine, I pulled off all the smog stuff, put headers on it and an Edelbrock 1406, man what a difference in fuel mileage and performance. The truck is now getting 15-18 mpg.

[terryj]

My emissions book doesn't have that Emissions code.

[rs72z]

The weights are under the rotor. You should be able to turn the rotor one way and it should spring back. If it doesn't one of two things, the advance is froze up or the distributor has ESC. Electronic spark control, if this is the case there will be a four wire weather pack connector coming from it. If it has esc throw it away and get a regular hei.

[Dan1969]

You have the weights. Just take the rotor out and you'll see a little combination right there



The Vaccuum advance just take it apart when you're doing the weights and spray it with carb cleaner and rinse, make sure the little arm moves with a little resistance, not too much. When putting all your stuff back together you will need to retime. Make sure you get a new coil as well and a module. I had an old 78 that the module would give me all kinds of problems.

[Cue-Ball]

It's important not only that the arm on the vacuum advance moves freely, but that the diaphragm itself works. When I bought my truck the vacuum advance didn't actually function because the rubber inside had broken down and torn. Not only was I not getting proper vacuum advance, but I was also getting a small vacuum leak thanks to the hole in the diaphragm. The best way to test is with a vacuum pump and gauge so that you can see exactly how many inches of vacuum are required to start advance and for full advance. But you can just suck on the vacuum line to check for leaks and proper operation.

[Dan1969]

You're right Cue-Ball. I'd say suck and blow on the little intake port to test it really quick.

[csb#356]

Could this shop have possibly not lined up the timing marks on the cam and crank correctly. I don't know if it would run or not with them not lined up but something to check I guess if you can't find anything wrong with the distributor

[donut]

I thought the '86's did have some sort of spark control?

1/2 ton I had years ago had the brain mounted above the glove box.

[rs72z]

Originally Posted by donut

I thought the '86's did have some sort of spark control?

1/2 ton I had years ago had the brain mounted above the glove box.

Pretty sure the 1/2 tons did not sure on the 3/4 though. A good pic of the dist. would help or just pull the rotor off and see if there is any springs.
Look at the pickup coil close and make sure that none of the wires are cracked and shorting out.

[motornut]

if you look close you can see the screws for the vac advance
my advance was rusted up bad,going to replace the dizzy soon,as it still sticks

[bulkin'up73chevy]

Ok so the holiday has set me behind. however I am checking like you said the timing marks on the crank to cam also the timing chain. It appears as though everything else has been in good order so far. Timing was 100% correct and the problem continued. Last thing I was to do is repair the cam but I just might have to go that route.

Also.... Spitting flames when running.

[csb#356]

If its spitting flames out the exhaust the timing is too far retarded I believe. This happened to me when my distributor was a tooth off but That wouldn't really make sense if the timing marks are reading correctly. Maybe your plug wires are in the right order but they are not in the right spots on the cap. Like you started one terminal ahead when putting them on. Id bring the #1 cylinder to like 8 degrees or so before top dead center and then look what terminal the rotor is pointing at on the cap and start there with your firing order and see what happens.

[motornut]

i hope they would have done the cogs when they did the chain but i've seen the
nylon gear teeth pull away from the gear,screwing up the timing,to spit fire
hope a steel one was used
how was the vacume advance?

[bulkin'up73chevy]

Ok update. I'll get pics later when the gf shows up with her good camera.

Timing dead on. vaccuum advance in good shape. weights working properly. There must be a form of ESC on it seeing as there is another unit in there i've never seen on an older truck.

Pulled plugs all in good shape with the exception of number 1. wire needs replacing however it was not like this before the shop and it was still acting the same then. so not the problem but will be fixed when I find my gapper. Then new plugs and wires. The shop also did not gap the plugs properly but again. Same before same after.

Oil change pulled the oil out. Looked good but smelled like fuel BAD!. It was also 2 quarts overfull. Again back from the shop like that. top her off just right. Also checked all other maintenance Antifreeze. belts. All in good shape.

I will get a picture of it but on the canister for the filter on the air pumps the center was all but gone! Says replace with part 700c. Doesn't match anything at napa or a general parts search or specific part for that year.

When I find my gapper I will fire it up again and see how she does after I figure all that i've opened up. If the same going to the drastic measures of a minor tear down.

I do have a general question. I asked a local buddy of mine what could be the cause and he said "If what you tell me is the way it's acting, it could be the lifters. If they don't fill with oil properly the valves wont open properly causing excessive pressure." e.g missfire &backfiring. Is this true? If so I have already purchased everything for a complete teardown quite some time ago in fact. I do apologize guys but this truck was made this way and I would like to keep it stock. No changes except to run better. My big truck i'll modify the hell out of but this did get 17 mpg. loaded or unloaded.

Thanks guys for your help. Any more advice?

[Ken 45LC]

Have you done a compression check lately? The only reason i ask is because i recently replaced a cam (thanks to this new oil) and I could not get it to run worth crap after it was put back together. Here the directions said to take it a full turn after zero lash when setting the valves. I found out that was incorrect and it wasn't holding enough compression. Readjusted the valves to 1/4 turn past zero lash and it started right up without any missing or jumping. So if you have a few valves that are over tightened, it will seem like timing when it really isn't.

At least it won't cost you anything to check real quick.

Good luck.