Hi everyone. We just finished driving 700 miles on our vacation and the van was surging every time you tried to increase speed. We took it to a shop who tested it and found that the fuel pressure was dropping from 28 psi to 10 when accelerating. They replaced the fuel pump and filter (external or main fuel pump) since this was happening on either tank. It ran good for about 15 minutes, but by the time we got back home, we couldn't even get up to 60 mph. Any ideas of what we should try next since it idles fine and just loses all pressure when the gas pedal is depressed. It sometimes shows on the temp gauge that it is running around the L in normal but we have replaced everything and had the temperature checked and it is 191 at the top hose and 120 at the bottome hose of the radiator. We will be replacing both of the temperature sending units, but I'm not sure if this might be making the computer cut the fuel pressure off or not??? Any help is much appreciated.

 

Sound like you are loosing voltage to the fuel pump, power or ground, Find someone that can do a voltage drop test to the fuel pump. I think the fuel pump is not running fast enough. Broken Wire

 

When you say voltage drop, are talking about using a fluke meter and having someone rev the engine while watching the voltage across the fuel pump harness? I'm guessing that it should be about 12v correct?

 

Hi everyone, this is babeedoll2u's husband. Voltage drop check was good. I checked while in neutral and revving the engine to about 4000 rpm, then put the van in gear and held the brakes and pushed the accelerator to the floor. Ran just fine this morning. I think the problem starts to become more apparent when the vehicle heats up...that's what led me to think maybe the computer was cutting off the fuel pump. I'm going to replace the temp sending units this morning and possibly the regulator since it's only 16 bucks or so then I'll put a post with the results. Any more suggestions as to what this might be would be much appreciated. Thanks, Jere

 

just a thought. are you sure about the fuel pressure drop.

when a car gets strange after heating up i think about the cats.

if you tap them with a mallet, they shouldn't rattle. if they don't rattle they could still be clogged up.

i think you can pressure test through the o2 senser hole. good luck. keep us posted.

 

me again. extra info on your van might help. no carb on that 86,right?

anyway i read all the posts here and alot of folks that have cat trouble tell your story.
it starts on a long trip.
power loss. cant get to highway speed.
filter replacement at some local shop.
things are fine for a few miles then trouble starts again.
seems to run ok when cold.

the smell of rotton eggs is a give away.

if this isn't your trouble(if you even run cats.) maybe this info will help some other reader.

 

also the fuel selector valve on these years are terrible. its a mechanical unit that uses the 10 psi pressure from the tanks pump to open and close these little valves that get stuck in all sorts of positions. they have o-rings that go bad.

this will cause fuel from one tank to fill the other as it returns to the wrong tank. it will cause that tank to fill and pressurise to the point of fuel pouring from the filler cap.

mine does this. i just don't fill the tank that has the return problem.

but, a few weeks back some one had similiar fuel issues that were resolved by replacing this part. he check it buy some how bypassing the unit.

not sure if this can help. on a long trip, changing tanks alot, the valve my be sticking or shot. it's a part to keep an eye on if fuel is moving from one tank to another. i think there was a recall.

 

okay, an update. It's definitely not a cat problem. I had the shop pull the o2 sensor and do a backpressure test. Everything is fine with the exhaust system...had to put a new o2 sensor in just the same. I pulled the fuel pressure regulator and replaced with another one just to be sure. Changed out the temp sending unit for the computer and then found the other temp sending unit. This one looks brand new so I don't think I'm gonna swap it out. Still getting the surging problem. I have no idea why the fuel pressure is dropping when under a load (in gear). The pressure gauge is reading 28psi when in park or neutral and I rev the engine. No real fluctuation there. I've read about the tank selector, but I'm pretty sure this isn't the culprit. Both tanks run til just about empty and then when I flip the switch, it goes straight to the other one with perfect fuel readings. I guess that I'll jumper the connector on the fuel pump and run a straight 12volts to it and run it that way to see if I still get a drop. That should rule the computer out. Could it be that I'm missing a vacuum leak somewhere, and if so any ideas on the culprit? Thanks for the replies. Jere

 

Next question, my upper radiator hose is hot, hot, hot, and the lower is cold. Fan clutch is new, thermostat is new, radiator is new but can it be blocked? How is a quick and easy way to tell if it's the water pump or if the radiator has some sort of blockage without removing the thermostat? There is no noise or weeping of the pump. Thanks

 

Maybe someone can verify this, on the Rangers in this era, they had a black canister stuck above one of the frame crossmembers that some had filters in and others did not, if yours has the filter, it could be clogged also, as far as the voltage drop, no you did not do that correctly, place Fluke meter in low voltage scale like .2 volt or 1 volt, start vehicle, place one lead from meter on battery negative and the other on the fuel pump negative line, see what the reading is, should be less than 100mv, do the same to the positive side, one lead to battery positive and other to fuel pump positive feed, 100mv max. this is a measurement of the voltage that is not making it through to the item that is needing the voltage, if your negative or positive side is above 100 mv then attention need to be placed on that wire for repair as a higher resistance than wanted repair, my thoughts here are for a fuel pump not up to speed because of low voltage, and also the voltage should be battery voltage running, which should be 14 volts or so, I am also questioning your fuel pressure guage quality. 28 is low, 35 to 45 is spec. if I am correct. Pinch off the return fuel line with the engine running and see if your pressure goes above 28 psi, Just had a vehicle in the shop where someone forgot to crimp the band clamps on the fuelpump hoses in the tank, fuel spraying past clamps and hose, caused low fuel pressure. Broken Wire

 

Thanks for the info. I was just going by what the mechanic had stated as far as the correct fuel pressure at the test point. It would never go above 30, even after changing the fpr. I'll have to check the voltage tomorrow as it is getting late tonight. The new fuel pump that was installed has a lifetime warranty so I might just have to swap that out. An update to the running hot issue...I took the radiator back and replaced it with a new one and same thing. I guess that it has to be the pump...no other logical explanation and there isn't anything left to change having to do with cooling except for the pump. I've heard a couple of horror stories about the bolts shearing off, has anyone experienced this? If no bad stories, I'll try to do that tomorrow. Then I'll only have one problem to deal with. As far as the tester, I just purchased it today and it looks like it is reading exactly like the tester the mechanic was using. I'll keep you all posted. Thanks again for the input.

 

i changed my rad a couple of months ago and had some similar issues. the temp would run alittle high and the gauge jumped around abit. i picked up a new therm. and temp unit figuring the rusty fluid i dumped out probably damaged the therm. and it couldn't handle my new rad.

but i noticed that it ran hot only when the heat or vent(on hot) was on.

long story short, i never got a chance to install them and the issue has since then resolved itself. i think it took the system alittle while to adjust to the new flow.

if you squeeze the top hose while the therm. is open, you should feel a surge of fluid as you let go.

if the problem started after a rad replacment, you might want to give it alittle time. my gauge would go past the L in normal and hit the peak really fast but would go back to dead center a moment or two later.

i feel for you with the multiple replacements. my rad. was no fun with the tranny coolers' plastic ties and all. i even stripped my new cooler fittings and had to break out a tap.

 

Update. Still getting het...doesn't run up then come down, just stays up around the a or l. Funny thing is sometimes it just runs right in the middle like it's supposed to. I'm going to attempt to change out the pump tomorrow night if the problem keeps up. I'm going to get back on the fuel pump again tomorrow as well...too many things to do during the week between work and home chores. I'll keep you all updated as to what fixes this silly thing. Jere

 

bigjerel,
I had a surging problem for awhile too.
It turned out being the negative wire going to the frame mounted pump.
Don't know what the fp was, but it's been working with no probs since I fixed the negative.

Patrick

 

Just wanted to say thank you for all of your suggestions. The problem with surging ended up being the fuel reservoir that is located on the frame just behind the fuel pump. After swapping out the pump, regulator, and the filter, that was the next in line. It was all gummed up and black junk came out of it when I pulled it out. Just as a heads up for anyone else, the fuel lines are no longer in production and you can't order them if something goes wrong. I had a really nasty leak when I put it together, but I was able to locate some o-rings that fixed the problem. I really didn't think that it was going to be the selector switch since I never had any problems with changing tanks. Huge difference in power now that I'm getting a good supply of gas to the engine!! The heating problem seems to have disappeared as well after changing out the radiator, fan clutch, both temp sending units, and the thermostat. My next project will be to swap out the exhaust manifolds since they are cracked. I'll keep you all informed as to the results of that little project. Hopefully it will go smoothly, but you never know when it comes to 20 year old bolts. Thanks again everyone. Jere