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I have a 98 GMC Savana 5.7L V8 engine. When it sits over night it takes forever to start in the morning. During the day it starts fine if it hasn't been sitting long before starting it again. The fuel pump activates when key is turned to on position. This van has new spark plugs, relatively new air filter, new fuel filter, and I've used about a half bottle of fuel injector cleaner in it. I don't see any fuel leaks and I've smelled the oil and it does not smell like gas.
I've taken pressure readings:
After running and then sitting for 30-60min: 0 psi
Key turned to on position: 62 psi and then slowly drops
Running idle: 52 psi
Normal idle psi: 60-66
I'm thinking either I have a bad fuel pressure regulator or a bad check valve in the fuel pump/defective fuel pump.
Any tips/advice/diagnosis would be greatly appreciated.
Thank you. I haven't tested pressure with engine completely cold yet, but I'm assuming it will be 0 psi since i tested it within an hour of running and it was 0. I have not measured amp draw. How do you do that? I have a multimeter. Will that single out if it is the check valve or regulator? The pump seems to work fine when it is driven. It's just in the morning when I leave for work when it takes a while to charge the pressure back up. I have been turning the key back and forth from off to on to get the pressure up and that seems to help.
That system is very sensitive to fuel pressure. As little as 5psi under spec will cause a no start.
Google - 98 GMC Savana 5.7L fuel injection diagnosis - go to the eighth result, an article from underhood service.com (it wouldn't allow a link). Lots and lots info good there. Hope it helps.
"When the key is turned off, the pressure in the fuel line should hold for at least five minutes. If the pressure drops off, the fuel pressure regulator or fuel pump check valve may be leaking. If pinching off the fuel return line produces the same results, the problem is the check valve in the fuel pump (replace the pump). If pinching off the return line stops the pressure loss, the problem is a leaky regulator."
I don't know the specifics on checking amps on this particular fuel pump. I guess just given the information you have posted, OP, it could be either a weak fuel pump or the fuel pressure regulator being "off". I would say check for any vacuum leak in the line to the FP regulator, but a vacuum leak on that line would make the pressure tend high, unless it's different from all the regulators I have seen.
Offhand, I would guess that if the fuel pump was weak, you would have poor running at higher loads, moreso than the pressure regulator, but maybe the regulator would screw with high-load running as well. If you have a safe place to tromp down hard on the "loud pedal", do that and post back up what happens.
3 steps as usual has a good test procedure. I'm hoping for your sake it's the regulator, most domestics you have to drop the tank to get at the fuel pump/integrated check valve. You may or may not want to tackle that DIY. I'd make sure to get the best fuel pump I could since it's a bear to change, relatively speaking. The OEM Delco part may or may not be the best thing - I don't know.
I think I'm gonna have a chance today to mess around with it so I will try to find somewhere in the return line i can pinch without damaging it. I am hoping it's the regulator too. That is a $50 part. A good fuel pump for this model vehicle is $250. I want whatever is cheaper lol. I wouldn't mind changing the fuel pump though. It's not the work I'm scared of, it's the price. I don't want to pour money into this vehicle. It has 233,000 miles. Just needs to last another 6 months.
TimBomb: It does have a cold start valve. I haven't tried that but I don't think it would help much unless the coldstart valve can hold it's own fuel pressure.
Thank you everyone for your replies. You've been helpful.
Okay I removed the upper manifold. Black buildup all over everything underneath. The fuel meter body appears to be secured to the lower manifold by only one bolt (which was loose) when there are spots for 2. The fuel pressure regulator has black buildup all over it. There also appears to be oil in there, which is probably due to the upper manifold gasket being bad. The fuel injectors are the ones that are like little clips with mini valves on the end and the other ends go into the fuel meter body. When I remove the little clips (similar to removing an electrical connector) the tips look clean where the fuel is actually sprayed out but the outside of them have the buildup all over them. It's hard to tell if one is leaking. They don't have o-rings. I'm thinking I'll just replace the regulator and clean out all the buildup I can. Has anyone had a similar job to this before? I know that it shouldn't be dirty in there.
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