1997 Chevy Cheyenne hard to start - sputters

Tiny
RODRAM
  • MEMBER
  • 1997 CHEVROLET CHEYENNE
  • V8
  • 2WD
  • AUTOMATIC
  • 209,000 MILES
My truck has been hard to start recently. (1997 Chev C2500 5.7L Vortec 209,000 km). This difficulty started in the winter. It needed a new block heater and I also had plugs replaced and the remaining ignition parts checked and OKed. The condition now is that it will take several attempts with the starter to start the engine: battery is good; fuel pump engages (can hear it for 2-3 seconds); starter turns over well when key is turned; it appears to try to start with a few sputtering sounds; after several attempts (usually 5 to 10 times) it will start and sputter for several seconds and then run fine.

I had it in a mechanic's shop a few weeks ago and they could not determine any cause for the difficult starting. No codes would show up, fuel pressure was good. They suggested it might be the fuel pump, but did not want to replace it because it actually tested ok for pressure at start up and running conditions.

Other recent work done in Jan 2009 was replacement of intake manifold gasket.
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Wednesday, May 13th, 2009 AT 10:07 AM

7 Replies

Tiny
PEAR69
  • MEMBER
What is the fuel pressure at start up? After start up? While running? And what is the pressure when the return line is clamped for a few seconds while running? How fast does the fuel pressure leak down after engine is turned off?
All of these tests must be done - along with a voltage drop test of the fuel pump - to rule out a failing fuel pump or fuel pressure regulator or leaking injector.

BTW - did you replace the fuel filter?
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Wednesday, May 13th, 2009 AT 3:36 PM
Tiny
RODRAM
  • MEMBER
Hey. Thanks for the reply. Your comments seem to be directed at fuel issues.

I am trying to remember details of discussion with the mechanic a few weeks ago, but I believe he said the fuel pressure was about 65 psi at startup, and at some point dropped to 52 psi, then back up to over 60 when running. I hope this makes sense. We had no discussion at all about fuel pressure when return line pinched, or after engine was stopped. I will get this all re-checked!. As well as voltage drop test at fuel pump.

I have a new fuel filter on the front seat of my truck (no good there, I know.) So I will try to get this on myself in the next day or two.

At what point might you think that the problem could be injectors leaking or sticking? I know these 96-03 Vortec engines have problematic poppet valves in the injector nozzle? I am bracing myself for this possible diagnosis>

And thanks again. I really appreciate this feedback
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Wednesday, May 13th, 2009 AT 5:25 PM
Tiny
PEAR69
  • MEMBER
In order for these fuel injectors to work properly they must have at least 58 PSI - 52 PSI is too low, and the fuel pressure regulator should never let the pressure get that low. Your problem is probably the fuel presure regulator.
The diagnosis of a leaking injector requires extensive and expensive computer analyasis. These poppet valve injectors are indeed problematic, and if you have the money, upgradeing them is a good option. The upgrade has no poppets to worry about and you will get a little better gas mileage. However, running some Cheveron Techtron fuel system cleaner through the system cleans these poppet valves.A little cheaper. Keep us posted
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Thursday, May 14th, 2009 AT 12:26 AM
Tiny
RODRAM
  • MEMBER
Again. Thanks very much for confirmation of required fuel pressure. Very difficult to start this morning again and I left the truck at my mechanic on the way to work. Asking him to check fuel pump, fuel pressure, etc. He said he would check a few other things as well and get back to me.

I have considered having the SCPI to MFI conversion kit installed to get rid of the poppet valve nozzles. But it is an expensive item and I would rather be sure that nothing else is wrong before I get the conversion done. Parts (in general) are far more expensive here in Canada as there is very little competition --- the complete scpi/mfi conversion kit with gasket for the v8 engine is about $350USD on gmpartsdirect. Com. (They won't ship to canada) and a local gm dealer here wants $900C (incl taxes) for the spider assembly without the gasket, and an independent parts shop here wants $600C, without the gasket. Also I have not even found a parts dealer or mechanic who knows what this conversion kit is until I explain it to them. So it could cost me a $1,000 parts&labour. I am willing to get it done, but I want to be sure that there is no other major fault. I know the conversion kit comes with its own new fuel pressure regulator. So if it is the faulty regulator on my truck I may just go for the conversion right away.
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Thursday, May 14th, 2009 AT 10:39 AM
Tiny
PEAR69
  • MEMBER
The conversion kit is avalible on Ebay. I am sure shipping to Canada will not be a problem.I get them for for around $350 USD. The kits include all the necessary gaskets and other parts.
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Thursday, May 14th, 2009 AT 11:12 AM
Tiny
RODRAM
  • MEMBER
I got the truck in yesterday to the mechanic shop and asked for another fuel system check. The diagnosis at the end of the day (from the same tech that worked on it 3 weeks ago) was. Rapidly fading fuel pump. So I left it there overnight and will pick it up later today. With a new fuel pump in it. Thanks for the information on the mfi conversion kit. I checked this out on ebay and actually at the moment the price is $280USD + $35USD shipping to Canada by UPS + duty, brokerage, tax when it gets here. I am still considering this injector conversion but want to look at issues one at a time. And decide whether to keep the truck for the long term.

Thanks again, I'll send another update
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Friday, May 15th, 2009 AT 11:42 AM
Tiny
PEAR69
  • MEMBER
The pinched return line test is the clincher test for a weak fuel pump. The pressure should spike to 75 or 80 PSI. If not replace the fuel pump.
VERY IMPORTANT -- If you do replace the fuel pump MAKE SURE the fuel pump chassy harness electrical connector is replaced also and the fuel pump ground is cleaned up. These two items are often overlooked and cause many problems after a fuel pump change. Be sure to remind the mechanic of these two items!
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Friday, May 15th, 2009 AT 4:17 PM

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