Jade m

Hi, I have been scouting here for months trying to fire up my 86 Aussie 928, I still haven’t driven it.

basically when I fire it up (which it fires straight up to 1000rpm or so), the rpms slowly go down to a stumble at about 500rpm and then it would die (maybe last 1 minute from firing to slowly getting worse to dying)

but it the real issue is that I think I have replaced everything I can.

so bought the car that had been sitting for 6 years, I take the fuel tank out, a bit gummy in there, clean everything fuel tank related and fuel hoses. Then did a complete intake refresh, compression good, installed a fuel gauge and 38 psi at low vac, 28at high vac, spark and fuel seem to make it to all cylinders, new vac lines, new gaskets, new idle air controller, new leads, new plugs, new temp2 sensor, new ign rotors, new caps, new ignition modules, ign coils, new injectors (4 hole ones), disconnected air pump and lines, refreshed all grounds and still pretty much just as bad.

have tried all the grounds, swapped/bypassed all relays and fuses, tried the maf (which is the only part that isn’t new) at different settings and also unplugged (still same result), and will be trying an ecu from another 928 very soon.

I would have thought it was running too rich originally, because as soon as I touch the throttle it would feel like it dumps heaps of fuel in and pretty much dies.
i only just bought a gas analyser, and chucked that into the tail pipe and found that the afr is 21+... so real lean, I only found this out a day or 2 ago, so I think that would narrow it down a fair bit I would think.

so what do you guys think? What else can I test or diagnose? I will check all looms with a multimeter (they all appeared fine, but I haven’t gone into detailed testing) and have a noid light coming too (although fuel seems to be making it to all cylinders)

ideas?

DeWolf

Did you replace the fuel pump? Jumper the fuel pump relay and disconnect the fuel line under the bonnet and place in a tin. See how fuel is pushing through

Jade m

No I haven’t, i have done a bench test though, think it was something like filled 1litre in 20 seconds, I thought it was adequate, and fuel pressure doesn’t drop at the gauge either

DeWolf

I've owned a bunch of 86 928's. Replace the fuel pump and filter and get rid of the in tank pump and just fit a screen. The in tank pump is probably full of varnish after 6 years. Also a known failure point.

You should also really get that maf replaced. Roger sells them rebuilt by Injection Labs. It will make the world of difference to how the car performs.

Post a pic of the car.

Jade m

Yeah I did ditch the in tank pump for a screen too, and just checked the fuel pump then, can fill a 2L bucket in about 25 seconds (from the fuel rail)



These are my other cars

Put the twists on them not too

DeWolf

When it starts does it run smooth or rough?

Jade m

Runs smooth for the first 10 seconds, and theoretically runs smooth until low rpms (500rpm). Sounds really sweet and fires up first turn. I would say that the usual starting “choke” the computer delivers the first few seconds

Jade m

Here is a video (I’ll see if it uploads, haven’t done it before on this forum)

DeWolf

Can you borrow a good maf from someone? If I had a spare one I’d send it you. Have you done the belt, pump etc? If you have I have the Porken 32V timing tool I can lend you if needed.