1992 Explorer power loss, surges -- pls help to diagnose

[larrydd999]

Dumb question... Can you hear the fuel pump running and, if so, does it turn off after a few seconds? I'm thinking a plugged fuel line or filter.

 

[2stroke]

I agree, I don't think the FPR could cause pressure to go to zero. If you pulled the vacuum line off, gas would be in the hose. You can replace it if you want, its not a bad idea. I don't see anywhere in the post that you can hear the fuel pump, but since you were recently driving it, I'll assume you can. In that case, check for kinked fuel lines, and replace the fuel filter. If that doesn't do it, then check for power and ground at the fuel pump connector plug. If that is good, then you have to pull the sending unit. Cutting and access panel is by far the best way to do it, and even if you opt the drop the tank, still cut the hole.

 

[pkn]

So, I think it was both: dying pump, AND extremely clogged filter.

1. I disconnected the fuel filter and measured fuel pressure on the filter's exit -- zero or almost zero.
2. I took out the filter -- it is severely clogged, I can not blow air thru it at all. New filter could be blown thru easily.
3. and measured fuel pressure at the filter's entrance -- first prime, pressure goes to 10-12 psi and quickly (~3-5 seconds) drops to (almost) zero. Two-three-four primings in quick succession -- pressure rises to 22-25 psi and quickly drops when the pump stops. Nowhere near the referenced 40 psi.

Filter and the FPR I will replace, but what to do with dying pump... I face an alternative -- drop the tank to replace whole pump assembly -- big project which I don't have time for... or retire my beloved boy and buy another one.

Looking at craigslist for 2009-2010 Explorer with under 100k miles...

 

[pkn]

OK, so I replaced the fuel filter and truck is running as before. I now doubt that it's running "normal"... but "as before". No problem accelerating anymore... at least during my quick 5 miles test drive.

I don't quite understand how can it be running with fuel pressure so low... or probably I don't understand something else. I don't want to check pressure right now -- engine is still hot. Will do when proper time. And then I will replace the FPR and check the pressure again. And only then I will start thinking about dropping the tank... or retiring my trusted friend.

Anyways, thank you all so much, reading this thread and others brought me much better understanding and helped tremendously. As this great forum always did.

 

[trashtruck]

dropping the tank isnt as bad as everyone makes out and takes less than a day with no experience, even with all this northeast rust. its better to have the tank empty. hardest part is jacking it up high enough to get the skid plate out and disconnecting the lines from the old pump. its better to go ahead and replace the entire assembly, your right there anyway.

 

[2stroke]

I don't know how many gas tanks I've dropped, probably about 20. The absolute best I did was on the most recent one, from Oklahoma and it took 2-3 hours. Those who claim to do it in half an hour, no way. It takes nearly that long to siphon the gas out. Dropping the gas tank is about equivalent to dropping the transmission. Its not "highly skilled" per se, as its just bolts, but everything is at an awkward angle. Its always something with a gas tank. Either the straps don't quite fit, those captured nut (u-nuts) break, and don't even get me started on those stupid quick connect fittings.

As I stated, with an explorer, there is a great alternative. Under the drivers side rear seat is the perfect spot for an access panel. Its quite easy to cut, and not nearly as dangerous as you would think. Plus once its there, changing a fuel pump can be done in 15 minutes. Once you are done you can either put back the piece you cut with tabs, or cut a slightly larger cover and screw it down. then its covered by carpet, and hidden nicely under the passenger seat.

Also, for future reference, on all vehicles, 30k miles is a good number to change fuel filters. I'm sure you could push it to 50k. The last one I changed was on a 2000 explorer that had been on there for 80k, and started to miss on cold mornings. I did all the usual maintenance and found the fuel filter to be nearly impossible to blow through.

 

[2stroke]

I don't know how many gas tanks I've dropped, probably about 20. The absolute best I did was on the most recent one, from Oklahoma and it took 2-3 hours. Those who claim to do it in half an hour, no way. It takes nearly that long to siphon the gas out. Dropping the gas tank is about equivalent to dropping the transmission. Its not "highly skilled" per se, as its just bolts, but everything is at an awkward angle. Its always something with a gas tank. Either the straps don't quite fit, those captured nut (u-nuts) break, and don't even get me started on those stupid quick connect fittings.

As I stated, with an explorer, there is a great alternative. Under the drivers side rear seat is the perfect spot for and access panel. Its quite easy to cut, and not nearly as dangerous as you would think. Plus once its there, changing a fuel pump can be done in 15 minutes. Once you are done you can either put back the piece you cut with tabs, or cut a slightly larger cover and screw it down. then its covered by carpet, and hidden nicely under the passenger seat.

Also, for future reference, on all vehicles, 30k miles is a good number to change fuel filters. I'm sure you could push it to 50k. The last one I changed was on a 2000 explorer that had been on there for 80k, and started to miss on cold mornings. I did all the usual maintenance and found the fuel filter to be nearly impossible to blow through.

 

[pkn]

Well, unfortunately, it's not solved. Today's driving: about 45 miles of mixed local/highway was "normal", and then the symptoms came back. Not as severe as it was, it seems, but the problem is there.

I suspect that the dying fuel pump throws its decaying guts into the line and clogs the filter again. I'll try to check the fuel filter again later today, will report.

 

[pkn]

trushtruck, 2stroke, thanks for the advice, if I decide to save my Explorer and replace the fuel pump, I would rather go by dropping tank. Replacing the whole assembly AND cutting the access panel along the way, of course.

Reason: I regularly feel gasoline smell in the cabin after sharp right turns, especially when the tank is full, so I'd like to inspect the tank filling pipes as well.

 

[pkn]

... 30k miles is a good number to change fuel filters. ...

I agree, but just wanted to mention that Haynes manual says that the manufacturer expect the fuel filter to last whole lifespan of the vehicle. Sounds like barely justified bragging to me

 

[2stroke]

Being from Texas, I doubt your steel lines are rusted. It is still worth a check for power at the plug. A bad ground could easily be the culprit. There is all kinds of mistakes in the Haynes and Chilton's manuals. I wont use either, the internet is a better source. Even the Ford manuals are BS when it comes to maintenance.

 

[pkn]

I took out the fuel filter -- it's clean. Clean gasoline comes out from both ends, air is easily blown thru.

Installed filter back in place, conducted fuel pressure check at test port:
After 12-13 quick primings (engine is off) pressure builds up to 20-22 psi and stays there after 10 more primings. After stopping priming, pressure drops to zero within 25-30 seconds.

That was with the old FPR. I'm on to replacing the FPR. Just because I have it.

 

[pkn]

With new FPR after 13 quick primings (engine is off) pressure builds up to ~17 psi and stays there after 10 more primings. When stopped priming, drops to zero in same 25 seconds.

Started the engine, at idle pressure rises to ~20 psi and stays there, dropping 1-2 psi while revving.

Looks like replacement of the pump is inevitable. At least, now I know the magic number to start confidently: prime it 13 times, and it will start like new

 

[natenkiki2004]

FPR should really only kick in at 40 or so PSI, I'm not surprised it didn't do anything. It's goal in life is to raise pressure when vacuum decreases so more fuel gets to the injectors. High vacuum lets more fuel bypass. When the engine isn't running (like before you start it but after you prime), you're getting full pressure to the injectors.

If I were you, I wouldn't prime that many times, just crank the engine until it starts. A concern of mine would be the on/off cycles of the relays and computer. 13 times every time you want to start the engine is a fair amount. Not likely to cause damage but un-necessary. If you REALLY want, you could run a jumper wire to the EEC test port for the fuel pump relay ground and run the pump whenever you want.

To be fair, it doesn't sound like the pump itself is to blame. Sounds like the check valve to me. The pressure shouldn't drop off that quick. The check valve is likely beyond wasted and is losing your fuel pressure. Bad news is, it's in the pump. Good news is, by the time you're done, you'll have a reliable fuel system for a while

 

[pkn]

... Good news is, by the time you're done, you'll have a reliable fuel system for a while

Yeah.. plus, I'll hopefully get the dashboard fuel gauge working again... for free. i.e., with no additional efforts to fix it!

 

[pkn]

I must add, I'm really impressed by the survivability of this truck. Half-dead fuel pump, almost completely blocked fuel filter -- and I was still able to move it!

I think it's the "blessing of being the 1st gen". Manufacturer did not have massive exploitation experience, and did not realize how low actually users expectations are, and it cared for reputation as much as for revenue. So, no corners were cut on reliability.

I remember similar effect was when Panasonic first released their mass-market DVD players. They put high end Faroudja deinterlacer and quality Burr-Brown DACs in a consumer-grade player. Just few years later you would only see those in videophile-level units. 10 times more expensive, of course.

 

[pkn]

OK, just to conclude this. I've spotted at local dealership a 2010 (last year of the 4th generation) Explorer XLT with incredible for its age 14 kmiles mileage. I could not resist the temptation. So, after short but fierce battle with the salesman (which I had shamefully lost) I became a next proud owner. My old beloved friend, the 1992 Explorer, will probably be on craigslist soon. I'm mourning.

 

[2stroke]

Keep up on maintenance on that 2010. Both engines offered in the 4th gen are pretty well know failures of ford, but will last if you take care of them. Too bad about the 92, but if you don't tow or haul things, the 2010 should be an improvement for you.