Rootsgroup

My first experience with a 944, we're fixing all the little things.

One thing I noticed, when the key is turned on w/o starting the engine, the fuel pump runs constant. Any other car with electric fuel pump I've seen, in doing this the pump will only run a few seconds and then shut down.
Surely this is not normal, could you let me know how yours works, and if this is not right, how to fix it.
I have no manuals as of yet, any help will be appreciated.\\
thanks,

Rootsgroup

nine-44

What year and model is the 944? that will make a difference, well, at least the year will. Sounds like a relay burnt in the closed position. If it's late it will be the DME relay, if it's early it will be called the fuel pump relay IIRC but I beleive the same part will work for either.

Rootsgroup

Thanks for the quick reply.

It's an 88na, and I bought it in your town.

GodSpeed

Welcome to the list. I'm shure you will find an ample amount of information here.

Rootsgroup

I pulled the DME relay, checked both swiches in it with a VOM, both open, no problem there. Appently it's being energized in error, or perhaps fuel pressure doesn't reach spec, or....?

tod84944

The fuel pumps on these cars should only run when the engine is cranking or running.

Neinfofo

I thought that my fuel pump ran with the key on as well...until I realized that I had my wipers on (after I replaced the wiper motor and never put the arms back on - yet). Sounds like the fuel pump working when they are on intermittent!

Just maybe....since this question seems to come up a lot.

Rootsgroup

Well, huh.

Called A friend w/a '86 944 turbo, he tried his key on engine off, said his runs full time as well.

Anybody got something rock solid on this?

Thanks for everyone's replies so far.

Rootsgroup

jpk

The fuel pump in all 944's will only run when the fuel injection computer (DME) gets a speed signal from the engine speed sensor on the back of the flywheel. In other words, the engine must be spinning before the fuel pump is turned on. This is one of the reasons that these cars usually require 2-3 seconds of cranking to start.

You're likely hearing something else. I believe the HVAC blower fan will run whenever the key is in the ignition. On the later cars (after '85.5, new style dash) even when the fan switch is on the off position, the fan runs on a slow speed.

It might also be one of the rad fans if you have a bad thermal switch.

The turbos have a small electric auxilliary water pump to help cool the turbo down; that might be what you're friend is hearing.

Pull the DME relay (fuel pump relay), put the key in and I'm sure you'll still hear whatever it is.

rberry951

Just to toss something else in the mix, you have no way of knowing what other previous owners have done. My new project is a prime example of shade tree engineering. It is quite possible that someone has bypassed the DME relay all together and wired the fuel pump directly off the ignition switch or other circuit charged when the ignition is on. The fuel pump sound will definitely come from the rear of the car if that is indeed what you are hearing. Turn the key on and go stick your head under the rear passenger side of the car behind the tire, that's where the fuel pump lives. If it's on all the time, follow the wiring coming from it and look for splices.

Regards,
Russell

SoCal Driver

Fuel pumps run under two circumstances; when the engine is being cranked the signal to the starter is split off to the DME and the DME closes the fuel pump contacts. The other circumstance is when the engine is running. This is where the 400 rpm limit comes from. If the engine drops below 400 rpm the fuel pump shuts off. The fuel pump is controlled by the DME.

If your fuel pump is running with the key on (check back behind the passenger side wheel well) then as stated in earlier posts either the prior owner has monkey farted with the wiring or there is reportedly problems with a different relay being used in place of the DME relay.

Pull the DME relay and turn the key on. Check behind the passenger side wheel wheel and see if the fuel pump is running. If it is then the PO has MF'd the wiring.

Rootsgroup

Thanks, JPK, I'm using your info...

And here's what I've got. Car's up on stands for waterpump and belt/roller deal, the cooling fans are on the floor unplugged. With ign. on, electric motor noise is coming from the rear. Pulled the cover from over the sending unit, put my ear to it, and the noise is VERY close. Then pulled the DME relay, tried again, noise still there. Then pulled electrical plug from sending unit (?) on tank, noise still there.

Now I'm thinking the pump is not "in tank". Also thinking someone's direct wired the pump.

What do you think?

Rootsgroup

Rootsgroup

Thanks rberry and socal, you posted while I was replying. I'll do some wire tracing once I can get the rear in the air.

Thanks to all,

Rootsgroup

Zero10

Fuel pump is below the tank, located on the bottom under a plastic cover.
There is a 2-pin connector that should be out in the open that you can disconnect to make sure the fuel pump gets no power.
Disconnect it and listen for the noise again.
If you're really dedicated, you could pull the fuel rail end cap and put a hose on the end, route it to somewhere safe then try turning the key. That would tell you really quick if the fuel pump actually is running.

jpk

If the cars on stands, just crawl under there and have a look while someone puts the key in. Behind the pass. side driveshaft, you'll see a silver canister about 3 inches across, 5 inches long. Thant's the fuel filter. Follow the line from the top (toward the outside of the car) back, and you'll eventually find the fuel pump.

I haven't looked on the 968, but on the early 944, it was a very obvious bright green.

Rootsgroup - you havn't mentioned the year of your car yet. It makes a difference...