Now i'm stumped.

[GAXB9R]

ok so here is what i got. my dad bought a 1988 Chevrolet 1500 with a 305 and 5 speed transmission. Truckran fine until the back fitting for the heater hose sheared off in the intake manifold. this led to replacing the intake manifold. repaired this and the truck ran fine. About a week later the fuel pump went out. No biggie take off teh bed and replace the pump (much easier than dropping a full tank of gas IMO)

ok so today we replaced the pump and the truck ran fine until it became hot. Once it was brought up to temperature it would die. Let it sit and it would crank back up. then it finally did nothing. This led me to think the ICM was overheating and causing problems. After inspection under the distributor cap it looked like hammered ass. Removed the ICM and had it tested. Tested bad as I had assumed, but the ditributor needed a new pickup coil as well. Instead of polishing a turd we bought a new distributor for just 40 bucks more than to rebuild it.

Placed the motor at TDC on #1 and set the distributor with the button pointing toards #1. Ran better, but still shut down once it warmed up. Checked the POS Bosch Platinum four prongs that were in it and they were carbon, oil and fuel fouled so some new A/C delco plugs were installed. I was sure this was the problem since I was getting fuel, compression and power to the plugs.

Well I was sadly mistaken because it would just turn over. During this duration of repairs at some point the engine began to spin a little faster than before. I was assuming timing chain?? but the button on the distributor still truned when the engine was rotated. Also the timing was checked numerous times and it seemd on point each time.

Now i dont know if the timing chain is stretched, jumped a tooth or just took the day off. Something in me says it is electrical (ECM), but a friend of mine is leaning more toward the timing chain. If anyone has any knowledge of this it would be much appreciated, because I am completely stumped.

Oh and yes all vacuum lines are connected and there are no leaks. I will say that the negative cable to the motor smoked a couple of times. Not sure why this is happening.

Thanks in advance.

[Zeroflat24]

It sounds like you have quite a bag of worms. I will say in almost 10 years of wrenching I have NEVER saw a major ground cable smoke. That would be #1 priority for me. I was a little confused by your post, are you getting spark?

[raz65man]

1988 small block--aren't the late 80's small blocks the ones that had the teflon timing gears? I'm leaning toward timing chain, especially if it has those damn plastic gears.
Raz

[Theycallmecrash]

Oh man! Right up my alley, id say trust me but dont! Get away from the timing chain, im fairly confident not your issue, the pattern and intermittent constant problem shows that. You have more than likely over looked something, related to ignition or fuel. My camaro thought TPI system damn near identical similar issue, my coil cause a spark but was so weak it would not light the fuel. What color is the spark? Fuel pressure psi? Any way to monitor data with a scan tool or not within your grasp? The is also an electronic spark control module external from the distributor, rare but they can crap out.

[GAXB9R]

are you getting spark?

Yes getting spark.


if it has those damn plastic gears.

I will definetly check into this.


my coil cause a spark but was so weak it would not light the fuel.

I had thought of this, but didnt want to just start throwing more expensive parts at it. Anyone know the proper way to test the coil?

Im leaning more towards electrical too, but wanted opinions over the night so i can tackle it sometime this week.

Aside from the fact everything seems to be breaking on this truck is ure do love working on it. i mean come on what car or truck nowadays can you sit in the engine compartment and work on it?? i also forgot to mention it is TBI.

[anrkizm95]

if compression is good timing chaing should be good,recheck the plugs for fouling.if they are fouled check your tps voltage voltage over 3.5 volts will cause a clear flood condition,check for strong spark ecm failure is also common.

[GAXB9R]

What color is the spark? Fuel pressure psi? Any way to monitor data with a scan tool or not within your grasp?

Spark is blue.

Do not have a fuel psi reading just yet.

I may be ale to borrow my friends snap on scanner tomorrow and run up and scan it.

[GAXB9R]

if compression is good timing chaing should be good,recheck the plugs for fouling.if they are fouled check your tps voltage voltage over 3.5 volts will cause a clear flood condition,check for strong spark ecm failure is also common.

Spark plugs are not fouled. I hve not checked the TPS as of yet. This is on the agenda now. thanks

I also forgot to mention we replaced the oil pressure regulator,because it was brittle as well. This was a portion of the fuel problem since it is tied into the delivery electronically.

[anrkizm95]

Do not have a fuel psi reading just yet. will it run spraying carb cleaner in the throttle body?

[GAXB9R]

will it run spraying carb cleaner in the throttle body?

did not try the crack for engines yet. You can cleary see that it is getting ample enough fuel. i now the other carb or starter fluid or ether gives it that kick. i just dont want to kick it to hard and it decide to give up the ghost.

[anrkizm95]

if you have good spark,compression,fuel and the ecm is good it should at least cough and pop if the plugs are not fouled again.compression should be at least/min 100 psi fuel pressure specs are 9-13 psi spraying can help determine if its fuel related without harming the engine.also have you checked for codes

[Theycallmecrash]

The proper way to test your coil is with an old fashion scope in the wires and measure spark voltage and duration, but a nice blue color spark says high volts, dim orange skinny spark= poooo!

Those TBIs can look like they are giving it fuel, easily visable injectors, those things should be sparying like sprinklers almost think it was too much fuel, thats why i say fuel pressure is? 15psi is what ya want. Your oil pressure sensor is a back up, for your fuel pump circuit, have you checked your fuses?

[GAXB9R]

compression should be at least/min 100 psi fuel pressure 9-13 psi spraying can help determine if its fuel related without harming the engine.
Gonna do this next go around.


those things should be sparying like sprinklers almost think it was too much fuel, thats why i say fuel pressure is? 15psi is what ya want. Your oil pressure sensor is a back up, for your fuel pump circuit, have you checked your fuses?

They are like sprinklers. When I first saw it I was like damn thats a lot of fuel. All fuses are good. Gonna check fuel psi next go around.

[anrkizm95]

Gonna check fuel psi next go around.
specs are 9-13 psi over 7 psi and the vechicle will run but poorly anything less than 7 and you wont get anything.these specs are regulated not deadhead

[Theycallmecrash]

Sounds like ignition timing. At this point. If any fuel builds up it should pop with spark and compression unless ignition is happening at the wrong time. Possibly the distributor skipped a tooth but unlikely, so without an ociliscope, you cant test the electronic spark control module. Replacing that only test ya go for it.

[bbletterin]

#1 is the fuel good,not varnished or discolored,,#2 to check t-chain turn engine with socket/wratchet clockwise and stop on tdc,look where dist rotor is pointing. Then turn crank with socket/wratchet counterclockwise and see how far it moves before the rotor button in dist. moves, if 10 deg or more t-chain could be a problem. Ive had bad gas cause problems that kick your butt cause it is old and dosent fire well or at all.You said that you reset dist. to #1 and they dont move,so t-chain would be a big concern for jumping.

[ReconLdr]

I would "Tap Test" the ECM before I did anything else. Just locate the ECM, start the engine and "Tap" on it with a screw driver handle. These vehicles had issues with the ECM circut boards loosing connection from vibrations and heat. If the engine stalls, sputters etc... when the ECM is "tapped" that should be your problem.

If the engine won't run, locate the diagnostic port. (It should be below the steering column in the center)

1) Use a paper clip or jumper wire and connect terminals A&B
2) Turn the ignition key to the run position, but don't attempt to start the engine.
3) Watch the Check Engine light:
A) Should flash code 12. In other words the light should come on for 1-2 seconds then go off for 1-2 seconds, then blink twice.
B) After code 12 is flashed, if there are other DTCs (trouble codes) they will be flashed after code 12 in the same manner. You just need to count the times the light flashes.
C) If the ECM won't flash code 12, (and you know the Check Engine Light works), check the ECM grounds. IIRC, you disturbed at least 1 ground when you did the intake/distributor swap. If the grounds are good, chances are your ECM is bad.

Note: Don't hit the ECM too hard. Think of it like knocking on someones door.....just have the screwdriver in your hand when you are doing it.

[stensg]

If you have fuel compression and spark you should be running. Dumb question but are your plus hooked up in the correct order? Do you have a timing gun to make sure you are set at the correct timing? It sounds like your not getting spark at the correct time.