Please help with my Mountaineer

[dalsox2235]

Hi guys, hope someone can help. About 6 months ago I bought a 99 Mounty with the 5.0 AWD with 71,000 miles. Everythings been great until about a week ago. It's been starting really hard, then when it fires up it sort of misses or hesitates for a second or two, and the idle will be real low, almost to the point of dying. I've been searching this forum, and so far I have cleaned the IAC, replaced the IAC, replaced the MAF sensor, and replaced the fuel pump relay. It idles and runs better now, but still the hard start and the misfires. I'd appreciate any help that can get the wife off my back!

 

[section525]

Have you changed the plugs and wires?

Welcome to the site.

 

[exploded99]

I agree with Section - do the plugs at least.

Is this a cold start issue only - does it idle OK and start quickly after it warmed up? Does it idle OK when cold after a few seconds of stumbling around?

 

['97 V8]

spark plugs and wire can do this. Also it could be the coils, but i have never seen one go bad yet.

 

[dalsox2235]

Well I think I have narrowed it down to hard starting after its warmed up. I can sit at work all day and it will start fine, 20 min. ride home, shut it off and 20 minutes later I have problems starting it again. I really dont want spend 3 or 4 hundred dollars if it could be a $50 fix. I appreciate all the recommendations I can get.

 

[exploded99]

Well, that sounds a little like a fuel pump issue - you will see some posts in here with hot start problems related to the fuel pump. They start to get flaky and people have hot start issues.

I think I would try a fuel pressure test - turn on the key when the engine is cold and see what the fuel pressure comes up to before you start it. Then warm up the engine, let it sit for 20 minutes so it bleeds off fuel pressure, and repeat the test. See if the pump is developing good pressure when you turn the key on with a warm engine.

Also watch the running engine fuel pressure after you start the engine in both tests. 99 V8's should be 65 psi plus or minus 8 psi according to my stuff.

Let us know how it goes!

 

[dalsox2235]

Where can I find the valve to hook the gauge up at? I kind of hope its the fuel pump, and not something like an injector or anything.

 

[MountaineerGreen]

Where can I find the valve to hook the gauge up at? I kind of hope its the fuel pump, and not something like an injector or anything.

On my 01,the fitting to hook up the pressure gauge is behind the passenger side coil pack, just to the right of the black plastic cover for the trottle linkage. It has a black cap on the fitting. You will need the smaller adaptor for your pressure gauge.

Im glad you were able to find the search feature....

 

[CDW6212R]

The fuel pressure tap is a schrader valve(tire valve). Have you gone through all of the tune up items? Those are all important, required, and save gas(money).

Change the fuel filter if you don't know how old it is, same for the plugs and wires. Also do you know how long the vehicle had set unused? Good luck,

 

[exploded99]

I'm not thinking injectors - I've had that. The longer the truck sits, the more gas drips into the intake from the leaky injector. You get hard starts in the morning with a leaky injector (leaks overnite). Start ups when the truck has only been off for 20 minutes or so are normal - the injector simply hasn't had time to leak much.

Plugs are still suspect unless you've checked / changed em tho.

 

[MTime]

Are you getting any OBD codes?

 

[dalsox2235]

I'm not getting any codes, and I've found that if I turn the key to the acc. position and back a few times, it will start up alot easier. So I'm kinda thinking fuel pump, but still not positive. I've changed the fuel pump in my old Blazer (piece of s#%t) a couple times, so hopefully this one isnt much different. If anyone thinks anything different, please let me know before I begin this adventure.

 

['97 V8]

drop the tank, pull old pump, pop in new o ring and new pump...lift tank back up...there ya are. all done

 

[CDW6212R]

A fuel pump is not an easy task, unless you've done many many of them, skip that until you know what the problem is. You can check the fuel pressure to know if the fuel pump is the problem. Your theft light doesn't ever blink rapidly does it? That would be a PATS issue.

Now then, my 93 Limited was hard to start many years ago. I discovered that turning on and off the ignition before start helped. That builds some pressure in the fuel rails. For about three years I always turned the key on and off twice, before the final on/start process. That was required any time the truck was cold.

I never worried enough to fix mine, but it was likely the fuel pressure regulator, or injectors leaking down too fast, not holding pressure.

Listen to the fuel pump when you firsat turn on the ignition. Without surrounding noise, you should hear it turn on for a long second. Try only starting the truck after priming the fuel system as I described above. If it works, then you have something not holding pressure well, or leaking pressure out. Good luck,