thomasmryan

Any chance supply and return are swapped?

951and944S

Is the fuel test port a cap and ball like the 944 or a schrader valve..?

Just put a tight fitting hose around the cap threads and do a short test run in a container.

T

951and944S

LOL, we shall soon see.....,

T

thomasmryan

fits the description

Otto Mechanic

I can't imagine how. The only part of the fuel system I worked on was the filter, which only involved the supply. The chance of the filter being in backwards is non-zero, but I checked the arrow direction again today and it's pointing the right way, towards the front of the car and away from the pump.

There's a chance it's just a bad filter I suppose, that's what I'll test tomorrow after the floor dries.

Otto Mechanic

Yeah, it's the same as the 944 and 928, but it's on the side instead of the end. I should have a 90 degree adapter to work with it in the mail tomorrow.

Otto Mechanic

Thomas; looking at the filter again I can't see a way the supply and returns could get confused, the return goes right into the top of the tank and doesn't have any fittings on it that could be used to connect it to the filter. Even in a drugged stupor I don't think I could have managed it

Otto Mechanic

What might have happened though could be I damaged the intake line to the filter while I was changing it. The lines look original. I used vice grips on the inlet hose after wrapping it in a rag, then swapped the filter in.

I wonder if maybe a chunk of the interior of the line came off when I clamped it, got sucked into the filter and blocked it? I should find out when I take it apart tomorrow.

Otto Mechanic

Update: removed & replaced fuel filter today, which is a real bear after the trans. oil cooler is installed. Turns out it was just a loose fitting on the exit side of the filter, tightened it, started the pump using the DME bypass method mentioned earlier (jumpering pins 30 & 87b on the relay) and ran it for about a minute with no leaks.

I did use an air gun off the compressor to blow out the filter, there were no obstructions and it was full of gas, which tells me the pump isn't just making noise, it's really moving gas and the gas is going past the filter.

I'd carefully planned to replace the filter while I had everything rear of the clutch out a couple of years ago, but neglected the "perversity of the universe" truism; if you do it the easy way the first time, you get to do it the hard way the second. There seems to be no beating this rule.

So I'm back to waiting on parts to connect my fuel pressure gauge. The problem is looking more and more like the DME.

Otto Mechanic

Update: I got the 12x1.5 to 1/8" NPT fitting today after removing, inspecting, reinstalling and leak testing my fuel filter.

I installed the new fitting and fuel gauge (see attached photo) then jumpered pins 30 & 87b on the DME relay to check pressure at the rail. I got 52 psi on the gauge. Spec is 55 +/- 3 so I'm at the low end, but the gauge leaks so I think that's OK. There's no longer doubt that fuel is reaching the rail at a usable pressure.

I didn't try starting the car because the lashup I used to get the gauge in leaked like a sieve and I'm waiting for all the leaked gas to evaporate. In another few hours I'll remove the gauge and try to start the engine again.

At this point I've tested:

- Spark. OK using a test plug.

- Injector Signal. OK using a noid light.

- Fuel Pressure. OK Using the pictured gauge.

If the engine fails to start on the next attempt, I'll probably repeat the noid and spark tests just to be sure. After that, if it still doesn't start, I think I must conclude I have a DME failure?

Thanks for any insights,

Scott.

PS: The "orange peal" on the valve cover is the result of having the inlet tube of my Motive power bleeder fail overnight while I was bleeding the hydraulic system a few weeks ago. It echos the damage done to the floor of my shop when the fuel filter fittings leaked during this diagnostic procedure. So now I get to re-finish my shop floor and my valve cover. That's what I like about servicing these cars myself; they give my life purpose...

PaulD_944S2

I would suggest you read the fuel pressure while it is running, or at least cranking.
You need to know what the fuel pressure is when it's running, not static pressure.

Otto Mechanic

A good test Paul, but of course once it's running I'll probably lose interest in the followup Sorry but I couldn't resist that one.

Unfortunately the "lashup" of parts I needed to measure the static pressure is so fragile (meaning it leaks like a big dog) that I wouldn't dare use it to measure working pressure. I would likely die in that process. I think I'll try a less adventurous approach to start.

Once it's running? Well I consider that "tuning" and since the car is destined for the track I'll very certainly pursue that line of investigation in the future.

Best Regards,

Otto Mechanic

Well it starts now. Not just a little; it really starts. Scary. Runs right up to redline and I have to shut it off in seconds.

Somehow it's acting like it's at WOT as soon as I turn the key. No more fuel problems, I think I've eliminated the DME?

Starts right up when I turn the key and zooms to about 8000 rpm without touching the pedal. Who would have thought a simple R&R of the fuel filter would have done something like that?

I'm completely mystified now...

jderimig

Where is the engine getting all that air to let it run to redline on start?

Tiger03447

Glad to hear that you got it started and no more fuel leaks! Watch out for gas fumes though..Those are what really get you. Even though the gas has left the shop floor, and is no longer present, be certain that the fumes are totally out of the shop. The fumes penetrate your clothing and get right up next to the skin. All is takes is a spark, and the right air fuel mix and you will be a crispy critter..and I truly hope that you don't have a gas fired water heater anywhere close to your shop...many houses have been lost due to that..just sayin..On another tack, your DME may still be bad...if you have a buddy that you can test yours in his car, that would let you know what the problem might be. Then you can send it out for repair or get a good one from somewhere else. following your situation and hoping for the best for you..