gasoline does not mix with open wounds

herr_sparky · Post by **herr_sparky** » Mon Apr 22, 2002 7:55 pm

heres an interesting problem: the other day the fuel pump stopped pumping, and after crawling around it looked like the fuse had blown. so I popped a new one in there and went on my way. fuse #2 blows in about two blocks and now Im thinking that I have a real problem. in goes a 16A fuse and I turn the car around to head home. I went through five fuses before I finally ran out a few blocks from home and walked the rest of the way. the next day, I walked the few blocks to the car with a bag of tools and crawled under the thing to have look, and after an exhaustive series of electrical tests for continuity, resistance, voltage, it seems it may be an internal mechanical resistance thats drawing too much current. Out comes the old pump w/filter&damper&hoses, in goes the same cluster from the running-fine parts car in the garage. but not before I forget to clamp off one of the fuel lines and spray gallons of gasoline all over my face and the street. In the frantic scramble for a screwdriver to loosen the hose clamp to allow the hose to slip over the filter neck, it slips and takes a chunk of my forehead with it, which is now accepting fuel. good times. when everything was snugged up and ready to start, the fuse blew again. replaced. now the damn thing doesnt even come on, nor does the fuse blow. More electrical tests and swapping out of pump relays, including just jumpering straight from the battery. no good. the old pump, when hooked up to 12V on a benchtop, operates and delivers the proper amount of fuel. So now Ive got power reaching the pump , sound wiring and relays, and a functioning pump on the bench, but once installed it blows the fuse every time, although under inconsistent circumstances. sometimes right away. sometimes after several blocks. Also another pump that appears to have frozen up inside after a few months of inactivity, but does not blow the fuse when given juice, it just stops drawing power. None of this makes any sense to me.

3rd_slow_411 · Post by **3rd_slow_411** » Tue Apr 23, 2002 10:09 am

Don't forget to check your fuse panel, especially if you have had water inside the car or really humid weather. It could be corroded or broken even, especially after yankin' around with it. Wd-40 may help if corroded and / or wet.

3rd_slow_411 · Post by **3rd_slow_411** » Tue Apr 23, 2002 10:16 am

Is the support bracket isolated from the body? If I remember correctly, it appeared to be.

LeeM · Post by **LeeM** » Tue Apr 23, 2002 6:36 pm

Oh, what a horrid tale of woe!

Two suggestions:

1. Unplug the electrical connector to the pump & leave the ignition switched on... does the fuse blow now??. If not, then it suggests the wiring is OK. If the fuse does blow, then you have a short circuit, (albeit intermittant), somewhere in the supply to the pump, and need to locate it.

Personally though, I subscribe to possibility 2......

2. Odd electrical problems that seem to defy logic are almost always caused by a poor ground connection somewhere. Check the pump's ground connection using a resistance meter if you have one, (remember that it might be an intermittant poor ground though). The ground wire will be coloured brown.

I cannot remember if the pump has just the two wires going to it or more... can you advice please.

Very best of luck with it.

Lee

ps... sorry if any of this sounds dead obvious.... no offence intended

herr_sparky · Post by **herr_sparky** » Fri May 03, 2002 6:22 pm

the latest: after sitting for nearly two weeks, I tried to start the car again this morning, just turning the key. Two interesting things happened: One, the fuse did not blow, and the pump ran for the one&half seconds its supposed to. Number two, when I cranked the starter, the engine started, then I placed it in Drive, and the fuse failed. I did this a couple of times with identical results. So I grabbed the good book, a bag of chips, and my multimeter and sat down for another round of electrical diagnosis. Out came the ECU plug, and one by one I checked the pins and their associated connections throughout the system. Along came pin #19 and fuel pump relay #85; continuity check showed that the wires for 85 and 86 were reversed. corrected, plugged back together, turned the key, and drove back home. Back when all this started, I did try several different relays, and its very conceivable that I just plugged them in wrong and just continued on my way, unsuspecting. The odd thing is,at the moment of the first failiure, everything was hooked up correct and had been for years, so I cant conclude that that was at fault initially, it must have been something else altogether, although having nearly identical symptoms. The long, hairy story of how all the power is supplied and regulated throughout makes all of this seem just barely out of my mental grasp. The pump originally in the car runs fine when hooked up to power on the bench, but how to test for how much current it draws, and seems that would be inconclusive without being installed and having a demand for current. The pump now in the car, taken from another that had sat for years,(a week ago did not even respond to 12V when jumpered direct from the battery termimals) now pumps fine, although very noisy. So my conclusions are that pump number one suffers from an intermittent internal electrical short that blows th fuse, and pump number two suffers from dirty old internal mechanisms that kept it from spinning and have since loosened up after being immersed in gas for several days. Finally, Im assuming that without the electrically flawed pump, the corrected wiring to the relay, and all the evidence Ive gathered from other tests, all should be well, but im still nervous, since I never really nailed dowm exactly what was at the root of all this. Anyone have any ideas on how I can pinpoint it?

rich2481 · Post by **rich2481** » Fri May 10, 2002 11:21 pm

A easy way is use a battery charger, most have a current meter on the front, I have used this method at times to trouble shoot different things, I also have a multi meter that lets me check up to 10 Amps,
I dont have any answers about why it did what it did though
sorry

herr_sparky · Post by **herr_sparky** » Fri May 17, 2002 7:12 pm

the saga continues: fuel pump 16A fuse continues to blow, following no pattern or logic. After seeming to have fixed the problem over a week ago, today I drove 30 miles on the interstate when the fuse failed and it took half a dozen replacements to make it home. Sometimes just turning the key does it, sometimes it takes several minutes, even hours. Sometimes Ill place a new fuse in, turn the key to "on", and while the pump is running for a second before starting, I can see the strip bulge and glow, but not completely spap, then its just a few more miles before it totally fails. With the key off, and the hazzard lights on, the gas guage swings from empty to some value and back again with every blink of the lights. this does not happen with the key "on", or when using the turn signals. All wires have checked out w/continuity and voltage supply, as Ive explained in earlier posts. Its been dry here for weeks and the inside of the car, particularly under the dash around the fuses, is free of moisture and/or loose wires. Ive not run out of gas for months, there has always been a minimum of the reserve gas in the tank, and the only other factor I can think of is that I installed a Pertronix kit about a day before all this started happening weeks ago. Its so enigmatic Im about to lose it and send it off to the crusher to save my sanity and just buy a corolla.

ray greenwood · Post by **ray greenwood** » Sat May 18, 2002 8:53 am

I had this problem many years ago. It has nothing to do with the fuel pump circuit. Next time it blows....make a note of what else does not work . The starter problem is pointing you in the right direction. The type 4 wiring system is very circuitous. Remember that when you turn the key, the fuel pump relay and timing circuit connects both the starter and fuel pump to power for an instant. Two things that can be causing high load (1) cracked ignition switch. Pull it out of the column and check..or pull the plug off the column unit...plug in another one, unlock the column with your key and drive it around and see. (2) There is in all models a live wire for when the car is running and one for when it is not running, that feeds your headlight switch. You will notice that when the key is not on...the headlights will not work...or the horn...or the brake lights. Thats a lot of load. In the 411 especially (I have had this problem in two different 411's) if the slotted ring that holds your headlight switch into the dash is the least bit loose...the switch will rotate around...intermittantly making contact with the metal dashpad backing....blowing #2 or #3 main fuse (16 amp) and either causing loss of fuel pump and several other circuits ...or casuing loss of all system power...including emergency flasher functions!!!. I had this happen in a short dark rail underpass in Oklahoma city a long time ago and almost got plowed by a semi. A sympton to check to know this is happening... even when it is running well...the #2 or #3 16 amp fuse stays really hot. After a while they can look like they are blown (kinda cooked ) even when they are not yet blown. Sound familiar? Check both your E-flasher switch and your headlight switch. They have a double slot in the threaded end of the switch body that actually aligns with dimples pressed into the metal of the dash to keep them situated so this will not happen. You cannot see this without removing the switch. Any lose trim ring nuts will cause this to happen. Ray