R31 Intermittent Fuel Problems

[coupe72001]

Howdy!

So, I have been getting around in grandpa's old stock as a rock r31. Things were going well, but I ran it low on fuel and it ran poorly for 30 seconds and died. I actually thought I had run out of fuel, so I topped the sucker up and it ran again.

Then it stopped running again the next day.

I drained the fuel tank, added injector cleaner and changed the fuel filter, and the car ran like a champ. Then it stopped again after 20 mins.

I decided I must have fouled the fuel pump and (being the weekend) I organised a couple of crappy 2nd hand fuel pumps, and the car ran again. Then it stopped again.

So I tried the other spare fuel pump and that went well for another 20 odd kms then it stopped. Again.

If I disconnect the fuel line at the filter when I start the car fuel sprays out everywhere. After a short drive the car dies, and when I disconnect the fuel line I get no fuel spraying anywhere. However, if I wash the car, or go for a couple of beers, or sit around for a couple of hours the fuel starts pumping again, and I can drive another few kms before breaking down again.

Do I have (now 4) dodgey used fuel pumps, that only work sometimes, or is there another problem - maybe like a bad earth, that causes the pumps to cut out sometimes then come back to life after a bit of a break.

Thanks.

[Ghostrider]

Drew,

I would be looking at the Fuel Pressure Reg & if that's not the issue try the injectors, but both of these don't explain the lack of fuel at the filter.

I had a similar problem with the KHR30 and I fixed it by chucking out both the old fuel pump and pressure regulator. Now it goes like a dream with a 910 copy fuel pump & right angle banjo fittings.

The R31 has an in tank pump set up, correct? If this is the go, look at the filter sock on the end of the pump, as todays unleaded fuel turns to nearly acid when it sits for a while and starts eating the fuel tank. The sock might have some rust & shit in it that blocks it up occassionally.

Cheers, D

[Birth]

You could try driving with a fuel pressure guage in between the filter and the regulator - that way you can be sure its a fuel supply issue and not something electrical.

[coupe72001]

Not even sure what a fuel pressure regulator is, but I'll look it up and try swapping it. The sock on the end of the in-tank filter looks ok. Besides, the problem is affecting multiple fuel pumps/filter socks, and at a glance they all look right.

[Ghostrider]

When you drained the tank, did you get much crap out of it and did you stick a hose in it and wash it out? When I first brought the purple DR to Sydney, what we got out of the tank was brown and we washed it out with a hose and let it dry out and then fitted a pre filter to be sure what was going into the pump was clean fuel. Works sorta like an intank filter sock.

Cheers, D

[coupe72001]

Actually the fuel looked pretty good, so I only drained, and didn't flush. Flushing and prefilter sound like saavy ideas. The r31 guys are suggesting that my crank angle sensor may be sending bad info to the ECU about when to send fuel. I'm going to try that, too. Apparently they are vunerable to malfunction when hot.

[Factory 5]

Exact same problem happened today on my mates R31. its stuck out on a work site in Melb, he has to get it towed.

no fuel pump priming or anything... seems like a common thig on R31forum

[blind_elk]

I heard of a similar story years ago with a Patrol. Long story short, there was a piece of plastic floating around in the fuel tank. Every now and then it would block the fuel pickup. After stopping the engine, the plastic would float away and everything would be OK until the next time.

As Dennis suggested, you might need to give the tank a really good flush.

Can't see the CAS stopping the pump, though.