mytrplseven

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As some of you may recall, I've been working on a resto project on my '86 951. Today I tried to start the engine after replacing or rebuilding virtually every component on the engine. Today I tried to start the engine and the fuel pressure was 32 to 33 psi and the Air Fuel Ratio was nearly 17! It took a little start fluid into the intake to get the engine to start and wouldn't respond to throttle application. The engine appears to be running expremly lean at idle.

To date I have replaced all the fuel lines, vacuum lines, fuel filter, regulator and damper, O2 Sensor, ignition system, rebuilt all the injectors, new intake manifold gaskets, AOS seals, one of the ref sensors, rebuilt the turbo, replaced two engine temp sensors that were bypassed by the PO, installed boost and AFR gauge (calibrated properly), cleaned the throttle body, no connectors were broken on the CV. Also checked all the other vacuum and cooling lines and replaced the cooling fan temp switch. The engine timing marks are right on.

The engine was running this way after I brought it down from the barn I found it in in Illinois but ran a good test drive before I shipped it. All I did was refuel the car with fresh 93 octane and then drove it home. I pulled the plugs when it wouldn't run and they were covered with soot and a bad injector was replaced with a new one when Witchunter sent it back with the others.

Since it started with a bit of start fluid but won't respond to throttle other than enough to trip the TPS, I'm wondering if the TPS is bad or if the fuel pump isn't putting out enough volume to run the engine. Could insufficient fuel delivery cause these symptoms?

Anyone have any relevant thoughts on this? It's got to be something significant and not some "glitchy" little irritant. Also posted on PP.

Tiger03447

Could it be the AAR letting in too much bypass air? Or the throttle blade being cracked open too much? Sounds like the fuel pressure is right in the range, and all the other parts have been repaired, or replaced, on the fuel side. The engine not wanting to run is confirmed by too lean a mixture and the AFR gauge. Either it's getting not enough fuel through the injectors or there may be a volume problem. Did you replace the fuel filter and the fuel strainer too? sometimes you can get the pressure right, but not the volume...might also be a bad or clogged up pump or fuel line. IMHO.

mytrplseven

I'm thinking along those lines. Unfortunately, I have a FULL tank of gas so pulling the strainer would be a bear. I bought an extra fuel pump with check valve but haven't tried to use it yet. I've considered this as the primary issue early on because if it wouldn't start without starter fluid, fuel delivery was suspect. I may have to siphon the fuel out and put it in the Boxster until I've removed it all and then get that part of the fuel system replaced. I did notice that the leak-down rate was erratic. One time it didn't leak down at all and other times it went down real fast so I'm losing confidence in the whole package back there.

The AFM was functioning good and was cleaned and wiper readjusted. But this issue reared it's ugly head shortly after putting in a fresh tank of premium so I guess it's possible there was some gunk in the tank along with a marginal fuel pump. Letcha know.

black944 turbo

Have you pressurized the intake system? It sounds a lot like an afm issue to me. I have had similar problems in the past. Every time my tps has had issues it has run ok.

mytrplseven

Planning on changing the fuel pump, filter (again) and checking the strainer first because this issue came on right after putting in a fresh load of fuel and the pressure readings, including bleed down didn't seem right. I put a moisture control additive in the tank in case there was any water in there. It was 9 degrees when I road tested the car so any water in the tank would have been frozen. I've had the entire intake system removed and all vacuum lines and seals replaced. Also opened up the AFM to ensure the wiper and internals were good. If the replacement fuel pump, filter and cleaned strainer doesn't fix it, then I'll consider the AFM. Also going to open the DME/KLR to make sure the chips aren't performance chips which would require a 3 bar FPR. The PO stated it was stock chip but you know how they mis-lead you sometimes.

mytrplseven

Wednesday: Pulled the DME to ensure the chip was OEM and not a performance one. Now changing the fuel pump and the replacement didn't include the copper washers for the check valve, so I had to order them, plus I managed to scratch the mating surface on the cap nut and didn't want to take a chance it would leak so made that replacement part of the order. Found a small leak in the intercooler so a replacement on the way.

mel_t_vin

There is no AAR on a 944/2...only an ICV.


That sounds 4 or 5 psi low to me...points to pump or FPR.

So, the FPR, FPD, and DME temp sensor are new OEM? But the CV, ICV, and TPS are probably still the OE, 30-yo, parts?

Why did you only change one of the two bellhousing sensors? Speed sensor input is required to run the fuel pump and [TDC] Reference sensor is required for ignition. Pretty sure either [bad] sensor will cause a no-start/no-run.

mytrplseven

I replaced it because the connector was broken. I was already into fixing things that needed replacing since I had the intake manifold off.
The fuel pump is being changed as we speak. Waiting for new copper washers and a new cap nut to finish the job.

Tiger03447

Keep us posted! Always looking for awnssers to potential problems on mine...when I get there..pokey bear, I guess.

mytrplseven

Replacement intercooler arrived Saturday and it was the usual high quality replacement parts I have come to expect from Larts. Well packed and air tight. He's my first go-to guy when I'm looking for parts for my project.