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1988 gmc: 1500 5.7 litre starts fine cold..throttle..wont start…

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my 1988 gmc 1500 5.7...
my 1988 gmc 1500 5.7 litre starts fine cold, but when warm after sitting a few minutes it cranks fine but is slow to start. If you give it any throttle at all it won't start.
Submitted: 8 years ago.Category: GM
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Answered in 1 hour by:
6/18/2010
GM Mechanic: kalamykid, Shop Owner/ Tech replied 8 years ago
kalamykid
kalamykid, Shop Owner/ Tech
Category: GM
Satisfied Customers: 5,593
Experience: I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
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kalamykid :

the first thing that I would check would be the ect "engine coolant temp sensor". If the temp sensor is reading to high then the pcm will not give the engine enough fuel to start properly.

Customer:

I changed the temp sensor, but that didn't help. I drove it till it was warm, waited 45 minutes & it wouldn't start. Waited 5 more minutes and it did start. This only happens in warm weather. Any other ideas?


 

kalamykid :

Did y9ou change the temp sensor or the ect? There are two different sensors?

Customer:

I changed the temp sensor, I think.....a 2 prong probe near the thermostat.....tell me about the ect...I don't know anything about throttle body fuel injecticon....I'm a carburator guy....do you have a phone #??? I will be glad to pay you or come to your shop....this is driving me nuts...I'm going to burn the starter up....thanks for answering.....


 

kalamykid :

Teh next time the engine will not start we need to find out if it is not getting fuel or fire. Do you have a can of carb cleaner or starting fluid?

kalamykid :

The next time it willnot start take the air cleaner top off and spry what you have into the throttle and see if it will start. If you are using starting fluid do not spay to much into it. let me know if it starts.

Customer:

OK.... the other thing I should tell you is that when it won't start it really smells stinky..like fat...or rich thanks for helping,,,,,,John


 

kalamykid :

DOes the check engine light come on and stay on after the engine is running?

Customer:

nope ...no engine light......I put a new jasper in it about 40,000 miles ago....my guy may have done away with the lights .... Im not sure...It runs great tilll hot weather.


 

kalamykid :

DO you ahve any complaints with the way it runs till you shut it off?

kalamykid :

Does the engine light come on if you turn the switch on but do not start the engine?

Customer:

nope...it runs great....yes the engine light comes on


 

Customer:

That was 5 years ago...I only drive it 6k a year.....it's a work horse ...plow snow ...no is the answer

kalamykid :

How old are the plug wires and plugs?

Customer:

not that old


 

Customer:

well....40,000 miles

kalamykid :

The first thing to do would be to do a full tune up including cap, rotor, wires, plugs and a fuel filter. If there is a lot of rust on the pick up coil under the rotor button then replasce the distributor as well. A rebuilt distributor will cost you around $60.00.

Customer:

That's kinda hard to believe.....this truck runs great except in hot weather....I guess I could try it & spend a couple hunred bucks, but I did alll that at the engine change. why would it not have a problem til 45 minutes after shutdown???

kalamykid :

When you shut the engine off the temp of the engine will rise before it starts to cool off. If the ignition module or the pick up cooil are weak " which you would get both with a rebuilt distributor" then the fire will not be there to burn the gas from the ignition system.

Customer:

I guess that makes sense....ok....I guess that's th next step...thanks for hangin' in there with me.....I'll stay in touch....hey,...what about the ect thing??.... Thanks, John

kalamykid :

The ect tells the psm what the engine temp is. The pcm then tells the injectors how long to stay open. The hotter the engine the shorter the time they stay open and the less fuel that is sprayed in the engine. If the pcm thinks the engine is cold then it will add more fuel. If the ect shorts out the pcm will think the engine is colder then it is and will add to nuch fuel.

Customer:

That explains the stinky rich smell....so you think a tuneup & distributor will fix it??

kalamykid :

I can not say for sure as I am not there to see what you have and not able to do any testing on it but from what you have told me tonight it is 80% that this will take care of your problem.

Customer:

sooo....how do you know if it's the ect, psm or distributor ???....based on your experience?.....also, I live about 40 miles from Kzoo...If this doesen

Customer:

work ,could I come there & you check it out??

kalamykid :

I am in chattanooga tennesse

Customer:

alright...thanks for your help.....I'll stay in touch....any tricks to changing the distributor??

kalamykid :

the best thing to do is to pull the cap and rotor button, then you can see the "star iner and outer rings" Line the points up so that they are point to point and mark the position of the rotor button. Then when you put the new distributor in make sure the rotor is pointing in the right direction and then line up the point. Tighten the distributor down and put the new cap and rotor button back on with the new plugs and wires.

Customer:

got it...thanks....if this works you'll get top dollar...thanks for working with me.


 

kalamykid :

You are very welcome.

Customer:

sorry for bein' such a pain in the ass..lol

kalamykid :

You have not been a pain at all. YOu just want your truck to run correctly.

Customer:

amen

kalamykid :

Get some sleep and tune it up tomaoorow.

kalamykid :

Make sure to use ac delco plugs.

kalamykid :

It will run much better with the correct pulugs in it.

Customer:

THANKS

kalamykid :

you are welcome.

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