a little fuel pressure regulator good times

[janderson4010]

I've got a 4.0 ohv in my BroncoII from a 92 explorer, its a great motor in a little bII and I've been really happy with it except an intermittent stalling issue i've been having. I use this thing for some pretty serious rock crawling, and occasionally it will start to sputter and stall on me like its running out of gas (its not, well not in the traditional sense). I've replaced both fuel pumps (I used the fuel system from the BII), the filter, the coil, cleaned the IAC and Maf, as well as new plugs and wires. No change except when I put a new high pressure pump on it the problem got worse.

So today I did what I should have done from the start, spent 20$ on a fuel pressure tester from harbor freight (it works but its kind of a pile of crap), and tested my fuel pressure. what I came up with was this, when I prime with the key I have 35psi that visibly drops, when I start I have about 31 and it goes to about 39 when I quickly hit the throttle. I realize this is in the acceptable range but when I let it idle for about 3 minutes to induce the sputtering stalling problem it dropped to less than 10 and then after about 30 sec the engine dies, and won't build pressure again for about 15 minutes.

now when I put this engine in I used the BroncoII fuel pressure regulator so that I could use my existing lines, the bII one has nipple on the outlet as opposed to being threaded, and I thought the pressure for the 2.9 was the same as the 4.0.

So the question is do I have a bad fuel pressure regulator or something else like a bad injector?(I don't think I do, looking for confirmation) And I need a fitting for the explorer regulator that will allow me to get a hose on it, does anyone know what thread pitch this thing is? it isn't 1/4" pipe threads, bk that would have been way to easy. I read through the fuel pressure regulator threads that I found on a few different searches and didn't find what I was looking for, any help would be mucho appreciated

 

[Maniak]

The 1992-1994 explorer uses that threaded on FPR.

The 1991 one uses that funky push on connector type thing which is the kind I think you used.

If you change that lower fuel line out for one from a 1992-1994 explorer you can use the newer (threaded), cheaper and most importantly, available one.

As for your other question...

Usually a FPR is always good or always bad.. The symptom sounds more like the Fuel pump,filter or collapsing line than the FPR.. At least to me..

It could also be something "in" the line that is plugging it up. You could disconnect the fuel line before the filter and turn on the key to flush that part of the line.. Then reinstall that one and disconnect it before the FPR to flush out that part of the line. This is of course assuming you know your fuel filter is good (they are cheap).

~Mark

 

[Turdle]

Psst.
I have yet to ruin a cheap air gauge I use as a fuel pressure gauge. Get the cheap dial type.


This will not work for checking pressure on the fly though. You have to hold it down tightly. But it will work to check basic fuel pressure.

Edit.
Fuel pump relay and socket. Check them for heat damage-maybe swap in a different relay.

Then check the ecm

http://www.explorerforum.com/forums/showthread.php?t=365420&highlight=pcm+capacitor

You could also have a weak connection at the fuel pump connector in the driver fenderwell. I think it is the blue one

 

[janderson4010]

I replaced both the in tank and on the frame rail pump, the tank was clean, I blew the lines out with compressed air at that time and also changed the fuel filter, I am confident then lines to and from the engine are clean. The relay is new, and I have switched it with other relays in the distribution box to no effect. the reason I believe that the regulator may be the problem is bk first it is not specifically the right one for this engine, and secondly I assume that if I had a leaking injector I would have a bank that was lean bk of the lack of fuel pressure and a bank that was rich bk of the extra fuel that was being dumped into the cylinder. But I am running lean consistently. I guess my next step is to pinch off the line coming out of the regulator(return), and if the pressure goes up it means that the regulator is bad, but if it stays constant I have a leaking injector. Turdle I have too used a cheap dial type gauge to test pressure, but this time I needed it to stay hooked up so I could get real time info on what my fuel pressure was doing during normal run and when it went to hell. Maniac I agree, I haven't really seen a regulator cause an intermittent issue but based on the symptoms I can't rule it out yet. thanks for your replies fellas, I really appreciate the input.

 

[janderson4010]

I just realized my elite membership has expired, oops, need to get that fixed haha.

 

[janderson4010]

one thing I guess I didn't post is that the with the engine off after having gotten my fuel system pressurized it bleeds pressure off very quickly, I can see the gauge go down, I am operating under the assumption that the fuel rail should be holding pressure for quite a long time, a couple minutes anyway. Anyone have any thoughts on that?