Extremely Tricky Problem

[TW1ZT3D561]

ok so i've been to 3 different automotive shops and none of them can figure it out.

 

so my next step is you guys i hope you can help

 

i have a 1997 GMC 1500 2X4 4.3L V6

 

symptoms:

 

doesn't start (or takes a VERY long time to get started)

but once its starts once, it fires up every time first try every time after that, unless i let it sit for 5 or more hours

then it doesn't start again.

 

i changed the battery and for some reason it started right up

didn't change anything but battery

 

then i let it sit at shop over night to make sure it started up the next morning after sitting for awhile

and to no ones surprise it didn't start up.

 

so i fiddled around with it some more and ended up taking off the distributer cap.

didn't replace it or even clean it off( it as replace about 6 month ago)

put it back together and it started right back up once again.

 

so again i let it sit over night at the shop.

came in this morning and it didn't start?

 

if i let it crank over for a few seconds and turn the key to the off position the motor spins backwards (like some old fords use to)

 

i ran a scan on it and nothing came up, there is no check engine light on.

 

if anyone has any ideas as to what it may be please let me know

or if this happened to you, let me know the solution

[McLeod]

I'd still lean toward the dist. cap being the problem. It may be work the $$$ to try either the best NAPA cap (or, OEM). If you get the NAPA, don't use the screws that come with it -- use the ones that came with your OEM distributor cap. I've just gone through a similar problem -- the dealer's best techs couldn't figure it out (....couldn't duplicate it, no codes;-), so I stopped by a shade tree operation that I've passed many times & they "solved" the problem for no charge by telling me that the cap was the problem. It was. Mc

[txab]

Check the fuel system. Filter, pump etc...

[jrod332]

has to be the fuel pump. I had the same issue with my S-10. Would take a few cranks to start it. Once it ran it would start right up after i shut it off. My money is on the fuel pump. Try banging on the bottom of the tank when it doesnt start.

[ChRoNo16]

Agree, sounds like fuel pump is failing to keep pressure in the lines. THe 97- Is that still TBI or had they moved up to something else? If its TBI- Watch and see if fuel comes out of the injectors, if not, you arent getting fuel to the top of the rail. All I can say is welcome to my world. Im having the same issues, and a month later im still stumped

[stlavsa]

Agree, sounds like fuel pump is failing to keep pressure in the lines. THe 97- Is that still TBI or had they moved up to something else? If its TBI- Watch and see if fuel comes out of the injectors, if not, you arent getting fuel to the top of the rail. All I can say is welcome to my world. Im having the same issues, and a month later im still stumped

 

Can you hear the fuel pump turn on when you have the key in the run position without the truck started? I would hope that one of the three shops would pick up on that.

 

 

It could be something with the distributor. I'm not sure how they work on these trucks but if there is a crank angle sensor, and its out of whack, it makes it hard to start. It could be electronic too, if a relay is messed up or cracked it will act like that.

 

If you can hear the fuel pump priming when you have it in run position then you can either start throwing parts at it like distrubutor, prolly not just cap and rotor. Other option is take it to an electrical place that can do some testing on it find your shorts or effed up relays, etc.

[stlavsa]

Re-reading your thread, since your saying it happens when its hot, it seems likely to be an electrical issue like a relay, and once its warm, something is expanding and losing connection?? something like that? And doesnt make the connection again until its cooled off...

[jrod332]

still think its the fuel pump

[stlavsa]

still think its the fuel pump

 

 

Ya its the first place to start for sure.. but like i said you should be able to hear it or have someone listen for it. What are the odds that three shops cant figure out a fuel pump tho? I mean if thats the case thats a terrible string of luck going to three totally imcompetant garages.

[Doug_Scott]

check the rotor inside the distributor. Take it off and look at the bottom side. Any black stuff there means you need a new one.

[Silverado4x4]

I say fuel pump also as it is loosing pressure after it sits for awhile and the longer cranks when cold as it is not building pressure fast enought to start until you keep cranking as the pressure builds to start, check the fuel pressure at the TB on a cold start.

[kdixer]

I would think if the fuel pump was not building enough pressure to get the engine started, then it will not have enough pressure to sustain any kind of high rpm's. He is not complaining of poor running, bogging or general symptoms of fuel starvation so I do not think it is the fuel pump.

 

I say let it cool and check to see if it is getting fire when you first try to start it. That is the best place to start. Pull a plug wire and insert an old plug into it and hold it near something metal on the engine while someone cranks the engine over for you.

 

If it gets good spark then it is likely fuel related. Cold start enrichment device (choke) is likely. Not sure what GM used in 1997. I know my 00' Dodge had an idle air control valve. A good throttle body cleaning might do the trick.

 

But I would verify spark first while it is cold.

[nickvrebel]

I say fuel pump, but it's not the inability to build pressure - it's the inability to HOLD pressure.

check the pressure on the fuel rail, I'd be willing to bet the pressure drops when the key turns off -there's a check valve in the pump that should hold the pressure. another way to test this theory is to turn the key to the on position without starting, allow the fuel pump to prime/ cycle, turn the key off, then repeat, this time after the pump stops start the truck. if it fires off that is the problem.