OK. Slits and I went over this, but more opinions couldn't hurt.

Symptom: Fuel pump quits after running for an hour or so. Pump is not hot to the touch. Let car sit for half hour, runs fine. Last time it crapped out and cooled off, I went to start it and relay fried. Replaced relay and it ran.

As I understand it, the things that affect the pump operation are:
Fuse 9
Relay and board
FI brain

Ron is sending me another relay board and brain to try. Anything else it could be?

how did your tow bar work?

Wasn't on a 914 but I had something VERY similar on my 944, turned out the multi plug going into the fuse box had been pulled and wasn;t reconnected completely. Car would run until the connection was hot and lost contact and would die. Let it sit for 45 min or so woould fire right up and do the same thing. Check connections?

I'll chime in with this tidbit.. motors under load pull more current... make sure your fuel filters aren't clogged, or that a chunk of something nasty didn't get into the pump itself. Gas flowing through it is cooling the pump so as long as you have SOME flow, it will not necessarily feel hot, even if it is being overloaded.


What does your fuel pressure look like when its running? Try looking at the pressure when you run 12 volts to the pump via jumpers. If you see a difference, you've got some problem in the wiring/relay/etc, otherwise, pressure won't change if the pump is blocked or crapping out.

Brian, Scotty, thanks for the tips. Back to the garage to check those things. Aaron, I didn't bother. Wouldn't start while I was at AAA to renew tags.

Went next door to 7-11, got a Slurpee, and let it recover.

QUOTE (Howard @ Feb 9 2006, 08:01 PM)

Brian, Scotty, thanks for the tips. Back to the garage to check those things. Aaron, I didn't bother. Wouldn't start while I was at AAA to renew tags. Went next door to 7-11, got a Slurpee, and let it recover.

hahahah....

replace the fuel filters and maybe pull the pump and take a look at it... see if there is any shit in it.


worst case scenario... move it to the front

Check all of your fuel system for obstructions. Even the tank. Rust in the tank, in the lines, line folded and kinked, etc... I've seen rust particle plugged fuel pickup from the tank cause exactly what you're describing.

So Howie your sure the fuel pump is not pumping?
It also sounds like a CHT issue I chased on the 73.
Car would start run fine for a period then cut out till cooled down then start over
Went down the same route IE started w/all the fuel elements up to including pulling the tank to eleminate and debris that "could" have been getting into the system.

For that matter...

Are you running a Pertronix in that car Howie?

Ha! Only 3 times???
I'm sorry but if mine had quit on me only 3 times I'd prolly still have it

No, really, sorry for laughing... I was always totally pissed after the 3rd time and I felt

Hope you find the problem before you buy a Miata

.....b

six.....

Eric

If you are burning relays, you are probably overloading the fuel circuit...
Get an amp guage inline in that circuit and check it while it is running...

Let it get hot and keep an eye on the guage...

Or, replace the pump and the filter...

Rich

Carlitos Way donated a pump to the cause. Will replace all and try to duplicate problem. New tank and filter, no Pertonix. Points are for real men, Miata's for sissies

Shit, I'll try doing a Rain Dance if you think it will help. I'm also starting to hook my long irons. Advice?

What he didn't tell you is that he found 2 of the four relays on the RB fried. He also didn't comment on the sound the relay makes when the engine won't start.

While I agree with the AMP guage inline with the pump, the thought was that the RB could be seeing intermittent contact with power to the relay coil...making a chattering sound as it just doesn't have the power to pull in. This could be the traces coming loose or exhibiting high resistance that supply the power to the coil when the board heats up due to current flow. Easy to change the RB to see if it "cures" the problem.

With the cost of a fuel pump at $400...it's worth investigating.

Also, in that circuit is the brain that controls the fuel pump on start. If it were experiencing a "heat" problem in the logic board, maybe it's cutting off the fuel too.

I still think that a CHT change might be in order. It to, could be intermittent.

Just a guessing game..........

That a whole lot different...

Just don't change too many things at once or you'll never know what happened.

It's been running at fast idle for almost an hour. Oil temp up to 180 (about as hot as it gets, big cooler). Can't duplicate problem. But some fun. Repainting license plate so it isn't so scroungy. And checked on board voltmeter. Lights on shows 10.6 volts; actual off battery with digital, 12.66 volts. Entertainment. Background on plate:

Slop on the yellow (touch up paint, mello yello)

Next step, when yello is dry, repray blue (latex base) and wipe off digits.

I had a problem with a relay board getting hot & not getting power to the fuel pump relay. Switched out the board with a known good one solved it.