wi54545

give the passenger side footwell a whack...

Matt Sheppard

Team:

Q1: likely that ref sensors are working due to bouncing tach.

Q2: yes, likely it has/had an aftermarket alarm (congratulations. . . ). If that is still in the works, you wouldnt be able to crank the motor soo likely not the problem.

Q3: you need to isolate whether it is spark or fuel that is the problem. Test for fuel pressure at the fuel rail and then you can go from there. Spark is just pull a plug, ground it on something metal and see if you have it or not when it cranks over. Your issuse with the fuel pump not spouting when key is on is a fail-safe in the design. Pump will only opperate when it sees movement at the reference sensors AND if the DME relay is opperational.

Clarks is your best source for troubleshooting, but let us know if it's fuel or spark and if it is fuel, whether injectors are not firing or if you have no pressure at the rail.

teamking

Thanks!

Definitely fuel is a problem.

I jumpered 30 to 87b on the DME relay for about 10 minutes and got about 3 ounces of fuel.

I have not replaced the fuel filter, so I guess I will order one. Clark's Garage also mentions the fuel pump check valve. Where exactly is it located and how is it tested?

teamking

Apparently, the 3 oz of fuel came from pressure that built up in the tank as the sun warmed the car this afternoon, because even with the jumper, there is no voltage at the fuel pump. I imagine the wiring has been chewed on somewhere.

I'm going to run an external 12 v to the pump to make sure it is working.

EDIT: The fuel pump did not respond to 12v. So I seem to have two problems.

951Tom

The check valve screws onto the end of the fuel pump. Sounds like you need a new pump, filter, and check valve. You probably have to rebuild the entire fuel system. If it builds oil pressure while cranking that is good. The oil pressure gauge sender could be bad, that light will cause the ! to come on.

teamking

OK, I read this thread <<https://rennlist.com/forums/showthread.php?p=4306365#post4306365>> last night. So, I disconnected my oxygen sensor and now I've got 12v at the fuel pump!

Now I just need to replace the fuel pump, check valve, and filter, repair the oxygen sensor, and troubleshoot the oil pressure sender.

My wife keep telling me that I enjoy the challenge.

teamking

OK, so I've been reading a little about oxygen sensors. So now I'm thinking that I could just snip the two wires to the heating element of the O2 sensor, and I should be left with a perfectly functional one-wire O2 sensor. I'll have poorer emissions during cold start-up but otherwise, should function perfectly. Does that make sense?

black944 turbo

Why would you need to take the wires off?

xsboost90

sounds like while fiddling w/ the o2 sensor, you wiggled the ref sensor wires, activating the DME and giving 12v to the fuel pump.

teamking

Yeah, I hadn't thought of that.

I did blow two fuel pump fuses (that fuse also runs the heating element of the O2 sensor), though, before I disconnected the Oxygen sensor.

I can't see how the ref sensor wires would have caused the blown fuses. What do you think?

teamking

Haaaaaaaaaaaahhhhhhhhaaaaaaaaaaaaaaahhhhhhhaaaaaaaaa

It's ALIVE! IT'S ALIVE!!!! IT'S ALIIIIIIIIIIIIIIIIIIIIIIIIIIIIVE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!




Since my last post in this thread, I've put a new fuel pump in, and found that it only worked when I jumpered pins 30 and 87b at the relay (but not otherwise).

I went through the clarks-garage procedure to troubleshoot the fuel system, and found myself resoldering the entire DME. That only took 3 hours.

Went to start it this afternoon and it still wouldn't fire.

So, I took out the DME/Fuel Pump relay and wired it up to an external power source and discovered that the secondary relay wasn't functioning.

So, I jumpered pins 87 and 87b (why does the relay need two relays anyway, since the one drives the other?), installed the relay, and the car FIRED UP!!!!!

I am elated!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

To get to this point, BTW, it's been 51.5 hours and $754.

dave1192

I did a Google search for Porsche shop manuals and came up with a web site in Germany where I was able to download a PDF version for $20 -- in English, no less. Don't know the site right now though.

Andy1212

A $700 "super" car, cant beat that.

jakomara

Tradebit ...Google it! $19.99 instant download of official 944 Porsche manual over 2000 pages. Print out what you need to do. Make a copy for your repair person or yourself. Try Bill Underwood's 944 world also.

Can't beat it!! Keep a cd copy in your car and use a laptop! Also get the Haynes manual.

Good Luck!

951Tom

[QUOTE=teamking]
So, I jumpered pins 87 and 87b (why does the relay need two relays anyway, since the one drives the other?), installed the relay, and the car FIRED UP!!!!!
QUOTE]

The DME controls the fuel pump via the relay. Glad to hear you got it running.