Fuel pump

[Sergei]

Quite typical - just when i thought "well, looks like this is it, no more fixing on the list" - looks my fuel pump going south.

Here is why: we went on loop of two trails, raising from about 6.5K to 11K, then back to about 6K and then up to 11K again. On the summit we stopped to consume some sandwitches and zubberfizz (very nice soda, made in Durango). So after that i am trying to start Disco - it turns over, but somewhat unwillingly. So i pumped accel. pedal for a bit and it got up. Well, it did look strange, but i figured it may have something to do with altitude. So i am starting to descend, and all the sudden, no matter how much i am pushing pedal - no revs, rough rough turning and then it dies. I opened tank, equalized pressure (sometime it happens on high altitudes that pressure buildup and altitude playing nasty games to fuel pumps), trying to crank it up - cranks slowly, then picks up, then dies. I can hear fuel pump working, then shutting off when key is turned. What makes me think that its FP - i am getting that FP noise many times in row, if i am not fully ignite, but turning key, waiting for pump to shutoff, then taking it out.
Long story short i managed to pump up enough using that trick so truck started and made it home (about 50 miles), but it scared heck out of me - dont wanna stuck in middle of nowhere on trail.

(new plugs, wires, fuel filter less than 1K miles ago)

So do you think i am right about FP diagnosis, and what is best place nowdays to get one?

 

[discomike]

Sergi,
You might want to spend some time and see if you can verify the fuel pressure at the rail when this is happening. The other thought is that if this doesn't happen at lower altitudes there is a good chance that the brushes are wearing out in your pump and you may need to replace it. Once they get thin it takes more power for them to fire the pump.
Good luck,
Mike J.

 

[Sergei]

Thanks Mike. Is it regular fitting on rail in there? I.e can one just grab pressure thingy in autozone or something like that and check? And what pressure values are normal?

I never did it before

 

[discomike]

Sergi,
I don't know the pressures but if you check it while it is running that will give you a place to start.
Recheck when it is acting up, it will be either be at near zero or bouncing around very low.
Mike J.

 

[Sergei]

Ok.. guess i just need to get off me **** and look it up in manual. I'll post here updates how it all turns out.

Thanks again, Mike!

 

[Sergei]

UPDATE #1:
i went to shop, got fuel injection pressure tester kit. Pressure after key is turned and pump shuts off - 37-38psi (gauge marked in increments of 2). Seems to be within specs. When truck runs (shifted over few gears, while standing. Unfortunately its hard to watch gauge - would have to run next to truck ) - 34psi or something like it. No noticeable fluctiation whatsoever.

When left alone (ignition off) - system depressurizing slowly over time, about few psi / hour.

Guess i will put new fuel filter in, order pump, and carry it around as spare... Unless something else would pop up.

 

[discomike]

What you need to be able to test is if there is any pressure at that connection when you are having starting problems. Just pressing in the pin and let bleed off when acting up will tell you all you need to know. The other thought is that the pressure shouldn't bleed down especially when it is not even hot. As the engine gets hotter there is a valve in the pump that is supposed to maintani the pressure, if it drops you will have starting problems.
Sounds like what is going on. By the way, what year is your truck? If it is a D1 you have a fuel filter, have you changes it?
Mike J.

 

[w00ht]

Sergei, I'm going to agree with Mike. High pressure fuel injection systems should not de-pressurize when turned off as this pressure is what allows the injector to atomize the fuel correctly (at least as far as I know). Don't count out that filter either. I have had a similar problem in a Toyota 4X4 before as well. Did all of the ignition stuff first and didn't even think to check the fuel filter (Toyota hid them up on the frame rail under the bed, FUN!), swapped out the filter and it ran like a top again.

 

[Sergei]

Yeah its D1 (1994), and yep - fuel filter was changed a bit ago, but since then i ran 44K twice through system, including motorvac, so there can be issue with it getting full of crap - new filter sitting on table, waiting to be installed.

And i ran truck few times today - started no problems, running - no problems. So i guess that this valve is getting old (no wonder at 135K) and cant cope anymore with altitude properly.

Here is my theory (after thinking, sticking fingers and rereading some old materials) on what i had there on trail:

we had infamous problem with pressure equalizing inside and outside of tank (i.e pressure inside tank dropped down (due fuel being sucked out, and not fully replacing with air + altitude change of about 2K(at first point of stalling), then 4K more (at second). Pump is about to ***** it, so she just wasnt able to cope correctly with sucking fuel out from tank and building enough pressure not only to start, but after starting - to mantain normal running..

So current plan - swap out old fuel filter (they are cheap enough to not even bother about cost) and order new pump assembly. So when damn thing will actually ***** it - i will be ready.

Thanks folkz.

 

[RoverChic]

This is the same thing that my Rover was doing. I am going to just replace the fuel pump.. I would hate to get stranded in the middle of no where. That just plain sucks. I will also change the filter too...