slight starting problem

[bludmon]

I have been having problems starting my 1994 Navajo. When it sits overnight and I go out to start it I have to crank it for a good 7-10 seconds before it starts up. Once it's running it runs really good and I can shut it off and restart it right away with no problems. It just seems like when it sits overnight it won't start up right away. Does anyone have an idea what would cause this? I also have noticed that while I'm driving and I put a load on the engine(or punch it) that the engine hesitates. But if I drive it normally I have no hesitation and it runs really good. Any advise would be greatly appreciated!

I have replaced the fuel filter already and the vacuum line going to the pressure regulator and it helped a little but I still have that problem.

 

[something9000]

sounds like the fuel system is loosing pressure overnight and thats causing the long crank time. and as to the hesitation it might be a vacuum leak or the fuel pump is starting to fail and not keeping enough pressure at the rail. try turning the key from "off" to "on" a few times before starting it in the morning

 

[bludmon]

I have done that and if I turn the key on and off about three times it will start right away. Does that mean I need to check for a vacuum leak somewhere? Or does it mean that my fuel pressure regulator is bad? Once it is running it always starts right up unless it sits for about 2 hours. Thanks for your quick reply.

 

[ERUSH97XLT]

Hello,

When you cycle your key a few times (without starting the engine), you are rebuilding fuel pressure in the injection manifold.

You are probably losing fuel pressure when the engine is off, as something9000 suggests. I would check for fuel leaks, proper fuel pressure regulator (FPR) operation, and sticky injectors.

Do you know if you have a returnless-style or a return-style injection system (I dont' know the manufacturing years of either, but others will)? The specific style will aid in pinpoint tests.

Do you have any performance problems, especially at wide-open-throttle?

Good luck,

ERUSH

 

[bludmon]

At wide open trottle it does hesitate but thats only when I put the pedal to the floor. Normal driving is fine. I do not smell any gas leaks either. I think it might have to do with the regulator because when I bought the car it had been sitting without being started for a good six months because the starter was junk and the person I bought it from didn't want to deal with it. One of the first things I did when I bought it was change the fuel filter and it seemed like the fuel that was in there came out like corn syrup even though it still ran. I'm not actually sure what your asking when you mention return or returnless injection system.

 

[arco777]

The 91-94 Explorer has a return style system. Don't worry about it.

Sounds like your regulator, but could always be the fuel pump. To test it for sure, a fuel pressure test gauge is a good investment and not that expensive. It will have a gauge and a length of hose with a "Ford Adapter" that screws onto a schrader valve on your fuel rail. It's easy to access and looks like a tire air fitting. Once hooked up you'll see in realtime the pressures.

When the key is turned ON the pump should pressurize/prime the fuel system. A properly operating regulator will hold steady pressure when you pressurize the system, so you should see the needle spike up to 30-40PSI and stay there without falling when you turn the key to RUN without starting the motor. This indicates the regulator allows the proper pressure and doesn't let the fuel pressure leak down. The rail should keep pressure for a while even with the key off. If pressure never comes up, you could have a fuel delivery problem with the pump or a very bad regulator.

With the engine running and gauge connected, punching the throttle should result in a tiny change in fuel pressure if any at all. If the pressure drops abnormally you have a fuel delivery problem such as a weak fuel pump.

After shutting the engine off you should still have residual pressure which lasts for a bit. If it leaks away real fast, the regulator may be to blame.

 

[bludmon]

I will definetly invest in one of those. Thankyou for telling me how to use it.

 

[bludmon]

Okay I went out and bought a fuel pressure regulator and replaced it and I'm still having some hesitation. So then I did invest in a fuel pressure test guage. When I hooked it up and went to turn the key to on(no start) the guage only went up to 14psi. As I said in an earlier post if I turn the key 2 or three times with out starting it and then start it on the fourth try it starts right up. I turned the key off and then back on and it went up to 24psi. Then I did it one more time and it went up to 30psi. Like I said before I put a new regulator on already.

Then I started the engine and at idle it holds at 27psi.when the car is running and I punch it the guage goes up to 30psi and then back down to 27psi when I let off.

Finally when I shut the car off the guage shoots up to 36 psi and holds there. Any Idea what all this means? I appreciate any help I can get but I have a feeling your going to say I need a new pump. I've pretty much replaced everything else!

 

[Roadrunner777]

Your readings are typical except the 14psi key-on reading. Yes, that's too low. If it were just the start heasitation, I might be tempted to just power the pump full-time with key on (some pitfalls to this that I am not mentioning here). But, you also note some engine performance issues, and that's going to take the pump.

 

[arco777]

Agreed with Roadrunner777. The pump should pressurize the system to ~30PSI on the first prime. Otherwise your readings are normal. Seems like a weak pump, given that you already replaced the filter.

You may want to look into the access panel method of getting at your pump. It involves cutting a hole in the floor but is easier overall. Check the pump's filter sock, and if that's not your issue you may require a new pump to cure the starting problem. You could just live with it and prime the system multiple times each start, but a weak pump will fail at some point.

Luckily, pumps for these cars are relatively cheap... I see a complete assembly for sale for $85 on one parts site I frequent, and online auction sites may have it even cheaper.