Yet another newb with a chattering relay...

[GoodSamaritan]

Hello all!

I am trying to repair a 1991 Tracker with the 8 valve engine for the old guy up the street and I don't have a manual.

There is a relay up behind the fuse block with a green connector that is chattering. (two pink wires going to it, cant remember the other two) Also the car won't start.

All the 15a fuses are good. (Checked with a meter)


After a bit of searching on your fine site, it seems that if it is probably the fuel pump or the ecm. I have swapped the relay already and jumpered past it without any luck.

Here is the funny part though, the chattering varies dramaticly whenever I turn on the headlights or the heater fan.

Also there are a couple of vacum solenoids out on the front of the engine that chatter in sync with the relay.

Is this the fuel pump relay I am dealing with or a bad ground, or???


There was a wiring diagram linked in an older thread here, but the link was dead.

[jtgh]

not a problem , i will send the full schematics now. to you. PM mail ,look in 5min.
that is correct, the green socket denotes the Fuel pump relay, the one next to it is MAIN.

the fuel pump is probably a dead short to ground.
internal brushes are worn to nubs and grounding out. end of life.

you will have no fuel pressure.
hot wiring the pump will blow a fuse.

the fuel pump draws 4 amps nomal, '


the reason it chatters is you are olverloading the circuit.
HL on lowers voltage and thus the chatter slows. quite normal during overload.

it could be ECU bad ,but first prove the fuel pump spins and gives pressure before
condeming anything.

it can be hot wired with a 15amp jumper wire ( 15amp inline fuse).
be aware if pump is shorted , jumpering it may cause the wire to burn in your hands.
the fuse is important when testing anything with a jumper wire.
BTW: ECU only engages FP relay for 3 seconds at key on.

and all times cranking.
and all times running.

those are the rule sets.

tell us more.

cheers.

[GoodSamaritan]

Thank you!

That is exactly the info I was looking for.

I was wondering if there was something loading the circuit down like that, but I had never seen one chatter like that. Everything else I have ever worked on just blew the fuse.

I guess GM/Suzuki/??? decided to cheap out on the wire sizes.

Also the info on your site in regards to rebuilding the ECM is valuable.
I've never seen an ECM so well documented.

Thanks again.

[brucebolivar]

Give me till Monday and ill have an answer for you. I know a guy who solved this problem, but I forget what he did.

[jtgh]

only thing to do is :
measure the pump current. if over 6-8 amps, its bad.
or hot wire it , and measure the current and or fuel pressure, its inside the tank , so taking it out is a pain, so most guys just check the pressure and the amps.
if out of spec, out it comes.

he did pull the FP relay and the overload ended, so that is pretty damin of the pump and that is the only load on that dedicted relay.

see attached schematic?

this problem is common , and he is correct the wire size is weak. so weak it dont blow fuse.

i think there are 20 posts for this in 2 years. here.

[GoodSamaritan]

Ok, made a little progress.

The relay chatters for much longer than 3 seconds. I suspect it would continue until the battery died, or you got tired of hearing it and turned off the key.

I ran 12v straight from the battery to the pump (didn't blow my 5amp fuse) and seemed to be pumpling a lot of fuel at high pressure.

Even so, the tracker wouldnt start.

I suspected the ecm, so I pulled it and opened it up.
Guess what I found? Leaky Caps and some corroded places. I could rebuild it in short order if I had the right caps handy. On the other hand I am working 60-70+ hour weeks and I really don't want to get into it. I seem to spend all my weekends working on everyone elses crap as it is. LOL Found a rebuilt one locally with a warranty for 350. It will be here monday.

I am still curious to know what you find out Bruce...

Thanks again.
Oh and if anyone needs help figuring out their 79-91 Crown Vic/Grand Marquis/Lincoln Town Car. PM me. If I don't know it, I can find it in short order.

[jtgh]

congrats you found it:
so far we have 3 fails for chattering FP relay or Mian.
1:ecu caps toast
2:Fuel pump shorting
3: wires and conns to ECU and MAIN and FP are all bad ,due to some crazy PO or Salt water leaking down crack in window onto ECU area.

easy fix:

in a pinch (other) get some radio shack caps. that corner CAP is crutial.
100 UF at 63vdc or 75v or 100v will work.
so will 120uf ,either num. a tad higher is fine.

or any local electronic shop.
also , any PC ATX power supply that is bad , ( i got 5 in a box here) I keep them
and pull lid and BINGO , nice selection of caps.

free caps are everywhere, old Cd player, Radio AM/FM old cassette player.
look in side.

in a pinch , you can find caps.
this size is very common, not rare at all.

then later , get some mouser or digikey 105deg. C caps. but if you live up north,
forget that.

[brucebolivar]

Ok I talked to the guy who had the problem and what had happened was the relay was chattering for a while. Then one day It would not start. He took the tank off and had every thing there checked and was ok. He had found a guy who ordered a computer from the states for $100 rebuilt. He put it in and it took right off.
That was the problem.

[Rhinoman]

The relay chattering is part of the built in diagnostic procedure. The ECU stores a lot of data in RAM and if a fault is detected it will restart itself and then reset the RAM to default values to try and clear the fault. So its power up, relays on, fault found, relays off, power down. Power up, relays on, fault found......
If the fault remains then the procedure is repeated ad infiinitum.

[jtgh]

always nice having blokes around with disassembled code to find that..
wow.
looping reset.

I have seen slow CEL flash codes, running like a slug.
most are bad capacitor on the main power input.
you get instant crashing ECU , with jumps to zero. over and over

disconnect inputs. to the ECU,
my 8v even starts with out the MAP, but runs rich as a pig.
I have pulled most of the senors, and all are mimiced,
but the TPS, (TPS is the fall back sensor).
same with 16v MAFS.
remove move them all but mAIN, FPrealy , injectors, and TPS.

the FSM shows all voltage on all pins , at idle, so if you need that, i can give it.

cheers