Fuel pressure problem

I have a 96 Suburban K1500 5.7L. It use to fire right up upon first start. Now it takes several seconds of cranking it before the engine starts. When it is hot, it is a little harder to start. I have had the fuel pump replace twice over the past 4 years and are concerned it might be going out again. These previous times the pump flat out died. So I trying to resolve this before I get stuck on this side of the road.

I checked the fuel pressure: 54 PSI with key on and also 54 PSI with the engine running. When I shut the engine off, the pressure goes right to zero within 20 seconds. The book says the pressure should be 60 - 66 PSI and hold that pressure for 5 minutes without dropping more than 5 PSI.

So, is the the fuel pump or the pressure regulator, or fuel injectors the source of this problem? I'm thinking that the pressure drops so fast, it is probably not the fuel injectors.

Anyone seen this before or have some advice?

If it is the fuel pressure regulator, is that a do it yourself or dealer type job?

Reply to
Danpperk
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Have you tried changing the fuel filter?

A mechanic told me a few years ago that on the older Vortec engines there is a check valve in line that requires a minimum of 56 psi fuel pressure for proper starting.

Lower pressure could be a dirty fuel filter or weak fuel pump.

Danpperk wrote:

Reply to
ronlin

Yes I have replace the fuel filter. Do you know where the check valve is located?

Reply to
Danpperk

Its called a pulsator, and its located in the fuel tank, the fuel pump connects to it, it connects to the feed line.

Whitelightning

Reply to
Whitelightning

Sounds like the regulator. You need to remove the upper intake manifold to get to it.

Reply to
calhoun

Reply to
ronlin

I would bet its the fuel pump. I have a fuel pressure gage in my 97 GMC. It goes right to about 65psi when you turn key on. Once started it idles at about 59psi and when accelarateing about 61psi and when really getten on it...its about 65psi. I had my pump go bad before I got my gage. It died at the gas station. Finally got it runnuning but lasted a week and died again. Pump was bad!! You can try beating on bottom of tank as your trying to start it. If it starts..... I would say its the pump for sure!!....From what your pressure is. Not enough to start it.

Reply to
Marshall

Here is a follow up as to the resolution. I replaced the fuel pressure regulator last weekend (that was a big job for such a small part). The pressure now follows specs peaking at 61 psi with the key on, 58 psi with the engine running and holding the pressure with the the engine turned off. The engine fires right up now like new. Before you would have to crank the engine several cranks for it to start.

Also, to the person that suggested the pulsator (aka fuel pump check value), my unit does not have one (per the dealer). Napa said they could not find the part number. Then I called the dealer looking for the part and they said none is called out. After I found this out I went after the fuel pressure regulator first instead of the fuel pump/pulsator.

Anyways, thanks to everyone for you inputs.

Reply to
Danpperk

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