Capt B

Hello
Being new to this site I am looking for some assistance.
My son's 91 Runner V6 developed a fuel line leak.
When he went to repair leak he found that the fuel line was in bad shape so he re-plumbed with rubber fuel hose and bypassed the filter in the process. Good old Ontario salted roads!!!!
After starting the truck it ran better than it ever did - for about 15 minutes then died on the side of the road. Towed him back to the shop and found the 15 amp fuse for the EFI was blown. Replaced fuse and engine fired back up. We left the shop and made it less than a mile down the road and blew the fuse again so we replaced it and fired back up and drove for another 6 miles and it died again. We towed it home this time and started investigating for no fuel or spark and found the 30 amp AM2 fuse was blown this time. Replaced this fuse and fired up the truck but it was running rough and would not idle then it blew the 15 amp EFI fuse again. We are suspecting that the fuel pump is grounding out, burning the fuse but are unsure. Anyone have any ideas as to where to look for this sort of problem or may have seen this before?

Sturmcrow

Am I reading correctly that there is now no fuel filter between the fuel pump and the engine? If so, I wonder if he plugged something up with sediment from the tank that is causing overpressure on the fuel pump and the fuse to blow.

scope103

The EFI fuse does power the fuel pump, among other things, so a short in the fuel pump wiring should blow the EFI fuse. In your case, probably an intermittent short.

The EFI fuse is NOT powered through the AM1 fuse, so that's being blown by a different short somewhere.

And sturmcrow is generally correct. Even once you fix your electrical problems, the truck will only last a few miles with a bypassed fuel filter.

Capt B

The fuse that blew was labeled AM2 not AM1 as you stated. We changed it and the truck fired up although rough and will not idle and blew the EFI fuse again. We will have to splice in a filter as the factory filter is rusted beyond recognition which was why he bypassed it.

Sturmcrow

The bad news is that just adding in a filter now is not going to help. I'll leave it to the other folks to tell you exactly what needs cleaning and replacing, but something is probably plugged up in the fuel system. My guess would be the fuel pressure regulator.

Unfortunately, the truck has 22 years worth of sediment accumulated in the bottom of the fuel tank. Normally the fuel filter keeps it away from the fuel injectors and other fuel parts.

Be sure to use a filter specified for use in a fuel injected vehicle. The little plastic ones are not designed to hold the pressure of modern fuel systems.

Please do be careful with the fuel system. We tend to take for granted sometimes that a small-seeming leak can turn into a fireball pretty quickly with gasoline.

Capt B

Is there a method for cleaning the fuel pressure regulator or is it a replace only part?

scope103

Fair enough, but EFI doesn't power through AM2 either. And if you're still blowing the EFI fuse, you've still got a short. And I don't think the fuse blowing has anything to do with sediment in the fuel system.

Also, I'm not convinced (yet) that you have a clogged fuel system; if you keep blowing the EFI fuse something else is wrong. But living in the Rust Belt doesn't help; if the fuel tank rusted through at the top and the filter rusted out completely, you could have problems. You just can't tell yet.

And if dirt in the fuel system is your problem, I'd expect a clogged injector or two before a problem with the FPR. But you can diagnose the FPR with a fuel pressure gauge once you can keep the fuel pump running.

Sturmcrow

Scope103, my reasoning is this:

If a clog in the fuel system could cause the fuel pump to overpressure, it might blow the EFI fuse. If that would not cause the fuse to blow, then never mind about the sediment causing the root problem.

A clog in an injector would not cause an overpressure, since excess fuel would still be diverted back to the tank by the FPR. A clogged injector would certainly make it run rough, as the OP also stated.

Capt B

on a further note to this issue, the fuel tank has been replaced before he bought it, he is at the point now that he wants to fix the head gasket in his other runner a 95 33re with a 5 spd and swap the engine and trans into this current one. he had to change the line from the tank to the engine with out the filter because the parts store was closed when he found that the line was leaking at the filter also.

scope103

I see no problem with the reasoning, but I'm not sure that the fuel pump alone would blow the fuse even if completely stalled. It just seems more likely that there is a wiring problem, given how much corrosion was found in that vicinity.

But we should all think this expansively. Was it Sherlock Holmes who said "Eliminate all other factors, and the one which remains must be the truth"? http://en.wikiquote.org/wiki/Sherlock_Holmes

Sturmcrow

I wonder if the fuel tank is nearly empty. I agree that a stalled pump would not blow the fuse immediately, but no flow would mean no internal cooling, and a near-empty tank would mean the pump could heat up and blow the fuse after a few minutes.

Of course, the simplest answer is usually the correct one, so a short due to corrosion makes a lot of sense. However, unless they nicked a wire while they were in there, the only thing that has really changed since the fuel leak was discovered is the tubing and a lack of filter.

I think the best line of action would be to check for electrical shorts first, followed by a measure of the fuel pressure at the rail (with the FPR in place). If the fuel pressure is off the charts (or zero, I suppose), that could indicate a clog.

Capt B

Tank was filled right after he replaced the line

Capt B

After replacing the fuel pump and doing some further investigation we discovered that during the fuel line change some of the wires from the O2 sensor had touched the EGR line and melted together, After separating them the truck now runs like a top, the melted lines were causing a dead short blowing the EFI fuse as soon as the key was turned on. I guess you cant keep an old 'Yota down for long. Thanks again for all the assistance in helping us sort out the problem.

Sturmcrow

Glad to hear its back up to speed. Were you able to splice in a fuel filter?

Its funny how a bunch of anonymous yahoos on the internet can make all kinds of postulations, but the answer is usually incredibly simple.