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Difficult to start 1997 JGC V-8

My son has a 1997 JGC, with V-8 engine. In general, it runs great, but he has a problem starting it the first thing in the morning.

On the first start of the day, it take quites a while to start. After it runs for a minute, he can shut it off and it will start up very quickly.

On the first try, if he turns the ignition on and off (slowly) several times, it will crank fine, on the "first" start of the day. If not, it takes quite a while to start up. He theorizes that this primes the pump, and allows it to start normally.

He suspects either the fuel pump or fuel filter. I understand they are both in the gas tank.

  1. Any general comments?

  1. Is there a method to "test" the fuel pump, once the tank is dropped ?

  2. If it is a clogged fuel line filter, would it be worth the extra expense to replace the fuel pump at the same time, because of the labor involved in dropping the tank ?

  1. Is dropping the tank on this model very difficult ?

  2. Is there anything "under the hood" that could cause this same problem ?

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My son will appreciate any helpful advice and comments that anyone can offer !!

Thanks !!

James

Reply to
James
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With the weather cooling down, the first thing I would look at is the battery to be sure it isn't a little weak, I'd also make sure all of your terminals and cables are nice and clean. I realize you think it may be fuel related, but what the heck, couldn't hurt to check it. It's that time of year anyway.

Reply to
Kate

Your description best describes a leaking backflow valve in the pump. This will allow fuel to drain back out of the lines during prolonged shutdown. The best way to check out the pump (and the check valves) is to buy/borrow a fuel pressure guage. A decent one runs under $20 - been so long since I bought mine I don't remember the exact price - and it's worth the bucks.

Hook up the guage to the fuel rail - there is a schroeder valve there to screw it onto. Ignore the initial pressure - it will mean zip since you undoubtedly let some spray while connecting ;)

Turn on the key - DON'T Start the engine. The pump should run for a while then cut off. If the pressure comes up but is still below about 40 PSI, cycle the key off and on a few times, leaving it on for a few seconds each time. The pressure should come up to 40 PSI.

Start the engine. After it runs for a short while, the pressure will drop to 30-31 PSI as vacuum builds up and pulls the regulator setting back. If you can locate the regulator - it should be on the fuel rail for that model - you'll see a vacuum line. Pull it and the pressure will jump back up.

Shut the engine down and watch the fuel pressure. It should stay above 20 PSI or so for at least 15 minutes. On my I-6, it was still 19 PSI after a week and yours should hold 15-20 PSI overnight. If it drops to or near zero overnight it means the check valve is leaking and the lines are empty so the fuel pump will have to run for a while to refill the line and purge any air before it will start - your description as the pump only runs a few seconds when you cycle the key.

To check the pump, the fuel pressure guage should have a setup to check the flow. You jump the fuel pump switch and see how much fuel the pump delivers in a minute or so. That tells you a lot about the pump - basically all you need to know. That's all done without doing anything but connecting the gauge - one heck of a lot easier than pulling the tank to get to the pump even with the $15-$20 cost of the gauge!

Reply to
Will Honea

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