No Start!

I was chasing down a "high heat all the time" problem this AM after I drove the car, then, 10 minutes later, after I figured out the heater problem (broken heater clip under dash) the engine cranks but won't start.

I assume it's something simple.

While chasing down the heater problem I wiggled a little the vacuum line that goes from the back of the valley cover to the heater valve and checked the vac line's connection at the back of the valley cover, I also got under the dash and found the broken heater clip. None of that should cause a no-start, right?

It cranks great, but there is no fuel smell from the exhaust so I'm assuming no fuel is getting to the engine. I have almost a full tank of gas.

I seem to remember that previously when I turned the key to "ON" but not "START" I would hear the fuel pump make a little noise, but now I don't hear anything at all when I do that.

Am I right in remembering hearing the fuel pump, or is my mind playing tricks on me?

If I am right, is there a fuse or relay for the fuel pump?

If so, where are they located?

Any other ideas?

Thanks!

Andy

Yup, turning the key to "on" makes the LS1 PCM run the fuel pump for about a second. Your fuel pump circuit depends entirely on how the PCM was wired into the car. The stock 944 DME relay, in the box under the cowl, is involved with operating the fuel pump and is a common point of failure. Hopefully your conversion bypassed or eliminated it. Mine did and I use a standard GM fuel pump relay mounted by the PCM.

Rich

Rich L. wrote:Yup, turning the key to "on" makes the LS1 PCM run the fuel pump for about a second. Your fuel pump circuit depends entirely on how the PCM was wired into the car. The stock 944 DME relay, in the box under the cowl, is involved with operating the fuel pump and is a common point of failure. Hopefully your conversion bypassed or eliminated it. Mine did and I use a standard GM fuel pump relay mounted by the PCM.

Rich

Thanks Rich.

I do have the DME in place in the box under the cowl, and I jumpered the relay terminals following [You must be registered and logged in to see this link.] instructions, but still have no fuel pump and no start.

But then again, I don't know if my conversion bypassed the DME and used the std GM fuel pump relay or not.

I feel dumb asking this, but I don't know where my PCM is mounted, is there a standard location? I don't see anything under the hood that looks like it.

EDIT: There is no fuse in the 944 location for the fuel pump, so I assume my conversion bypassed the 944 DME.

Heh, the usual place is underneath the passenger kick panel or behind the glove box. Mine is mounted on the passenger side of the transmission tunnel. And I have a fuse/relay panel mounted there as well which includes a GM fuel pump relay.

Rich

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OK, thanks, I was confused, I thought you were saying that you had the LS1 PCM in the car. Ya, my 944 Bosch PCM is underneath the passenger kick panel.

Anyway, as there is no 944 fuel pump fuse in the fuse panel, it seems that the 944 DME has been bypassed.

Any idea how to proceed now?

I have no idea where a GM fuel pump relay might be located, I did not see anything that looked like it near the 944 PCM.

acorad wrote:I thought you were saying that you had the LS1 PCM in the car.

I did, and I do. That's it pictured there while I was working on the wiring.

acorad wrote:I have no idea where a GM fuel pump relay might be located, I did not see anything that looked like it near the 944 PCM.

You likely don't have the 944 DME (that's German for engine computer) anymore. You probably have an LS1 PCM (that's Chevy for engine computer).

I'm afraid you're going to have to science-out exactly how the fuel pump circuit is setup. But maybe it's a simpler problem of switching or grounding or it could be the fuel pump itself. I'd go back and look around where you were messing with vacuum lines. It's likely you unplugged something or tweaked a wire while you were in there.

Good luck.

Rich

Ya, that's what thought. Thanks Rich.

Well, the car now runs.

I really don't know what I did, or if I really did anything. Which kind of makes me nervous that it might happen again!

I took the cover off the fuel pump and tried to pull the connectors off the pump but realized they look like they're probably permanently attached. Then I found a plug connector nearby and unplugged that to check voltage.

My buddy turned the key while I checked the voltage at the plug and it showed full voltage for a second or two, then dropped to zero. Which I think I read somewhere is what it's supposed to do.

After that I realized that the engine didn't crank while my friend turned the key, which was weird because it was cranking all day when I turned the key, so I tried to crank it over myself and not only did it crank but it started right up.

I guess my friend only turned the key to the ON position, not START.

Anyway, I hope it doesn't do this again!