1997 Vortec 5.7 difficult to start after sitting a while

[divorced]

1996 Vortec 5.7 difficult to start after sitting a while

Truck: 1996 Z71, Vortec 5.7

Problem: It doesn't seem to start as easily as it should. If we let the truck sit for about a day and a half it takes about 45 to 60 seconds or more of cranking the engine to start the truck. It starts somewhat ok if we drive it a couple times a day, but it doesn't start as quick as it should. When I turn the key on I can hear the fuel pump turn on and then hear the relay click off when the fuel pump turns off. So, where do I start? (I am fuel injection ignorant, so I don't know the location or purpose of many parts)

Edit: The truck runs fine once started, if it matters.

 

[1979jimmy350]

it could be your fuel pump realy. GM on the newer trucks uses a set of relays in case one fail. The second one is activated when the oil pressure hits 4psi.

 

[divorced]

Where is the second relay? I checked the one in the box under the hood near the brake booster.

 

[84zz4ss]

No Start

In reality there is only one relay. The prime you hear with the key on is pcm control of the pump. Once oil pressure or crank rpm are present the relay again is energized. If it were my truck I would check the fuel filter. The fuel pump also has a check valve to prevent fuel draining back to the tank. It may not be working and the pump has to run in excess to provide adequate fuel pressure. I have also seen the fuel pressure regulator leak causing extreme rich condition and extended cranking time.

Scott

 

[1-ton]

One thing you could try is replacing your temperature-sending unit. If it is not working properly, then it could be telling your computer that the engine is warmer than it is, and not letting the computer richen up the fuel mixture for cold starts.


Another thing could be a weak, but not yet dead, fuel pump. I have the same problem on my 1991 V3500 with TBI, and I think the problem is a weak fuel pump because I tried replacing the temp sending unit, and that did not help it much (only a little).

 

[divorced]

One thing you could try is replacing your temperature-sending unit.

Is this the one in the head?

 

[84zz4ss]

No Start

The sensor is in the intake next to the egr valve. The one in the head is for the guage. Not to step on toes but I do not think the coolant temp is your problem.

Scott

 

[divorced]

Ok, thanks. I will start with the filter, it's cheap and wouldn't hurt to replace it either. I may have a friend of one of my friends look at it. He has a fuel PSI tester, maybe that will help?

 

[84zz4ss]

No Start

When you get the guage on it be sure with the pump running pressure is 60-66 psi. When the pump turns off it should maintain 55-60 psi. It also should not drop more than 6-8 psi in ten minutes.

Scott

 

[6.2Blazer]

Do some diagnostics first........even a Chilton or Haynes can help.

The long cranking time would lead me to check out the fuel pump first. A pressure gauge can tell you if it's getting weak or not, and the anti-drainback valve or a leak also sounds like a possibility.

I suppose the temp sender could cause an issue, but I'm not sure how it works on this model. It did cause starting issues on my '90 diesel because it was fault and giving a high temp reading (wouldn't allow the glow plugs to cycle). At least on mine, simply unplugging the sensor defaults the signal to a "low temp" condition and triggers and allows the appropriate parameters for cold weather starting.

 

[sweetk30]

if the pressure drops then the spider is a big problem in these motors. the spider is the block in side of manifold that has the regulator and 8 tubes coming out of it and these attach to the injectors. lots of these are going bad now.

 

[divorced]

Update - Now the "Check Engine Soon" light is on. I'm going to take it back to the stealership we bought it from only 9 days ago.



First the wiper motor stopped working - I got it fixed for free at a GMC dealer because it was a recall item.

Then the heater control circuit board went out - the dealer we bought the truck from fixed it.

Then the starter goes bad - I bought one and put it on so Michelle could get home from work.

After I put the starter on it wouldn't start very easy, now the engine light is on!

All of this happened in the first week of owning it, I hope our luck changes for the better!

 

[sweetk30]

its a sign ... ditch it dude.