Trav

Hello I'm new to the 944 and forum world so I apologize if I'm not keen on etiquette I have googled and googled until my eyes burned countless nights. I just scored an 89' 944 because of a no-start and flex plate dampener issue. I started doing the normal checks spark fuel compression. When plugs and coil were replaced spark was attained, YES! Haha fuel is 31psi during crank (a little low recalling Clark calls for 36 +/- 3) compression is dead nuts 158psi across the board. I have pulse ( it didnt when i bought it, got a reman DME) injectors have power and appropriate resistance, new ref sensor, DME relay. Now I think it's as simple as fuel delivery pump and filter but before I throw parts at it again let me run the symptoms by ya. When I stop cranking it diesels like 2 or 3 cylinders, fuuhh fuuh fuh (sound effect). With the new computer I've gotten it to fire intermittently, almost rarely every 4 or 5 cranks but not regular like that. Possible timing issue ....? Thanks for any future help for the aforementioned

Rogue_Ant

Is the car consistently sparking?

Trav

To be honest I haven't checked it in a few days... I determined I had spark then moved on- cap and rotor if its not consistant?

Rogue_Ant

Cap & rotor is one thing.
The DME speed & reference sensors are another thing to check.

Fuel pump is something you can jumper:

http://www.clarks-garage.com/shop-manual/fuel-05.htm

So that would eliminate the fuel-pump from being intermittent.

Trav

It runs, fuel pump, plus I've had a gauge on it for a while just for curiosities sake but I've had a weak pump in a Z71 and a Jetta where I had to charge the line by running the pump a few times to get my 55psi the. It seemed to run fine. Usually they just crap out but i seem to get all the atypical problems. I replaced the ref sensor would a speed sensor cause intermittence?

Rogue_Ant

Yes, the speed & reference sensor should be thought of as pairs... if one is bad enough to replace, then other should be as well. Additionally, the wiring for the S&R sensors could be bad/dying, which will also cause an intermittent issue.

Trav

I probed for continuity on both harnesses all seems well there. I just ordered the speed sensor.

Rogue_Ant

Just probing the lines for continuity doesn't reveal much. Unfortunately for testing, the lines carry a low-voltage (at cranking speed) AC signal from the S&R sensors. Think about watching a TV on an old attena... you might be able to see the picture, but it might have a bunch of static...

Try the new sensor, but if your spark remains intermittent, then I would replace the wiring too.

Sentinelist

Agreed- if you get the speed sensor, get the reference sensor as well. I just replaced mine earlier this year.

Trav

Consistant spark but I noticed when jumping DME relay fuel pressure was even lower pulled the filter it weighs 3 lbs from all the debris haha trashed a line, of course, removing it... Would it be rediculous to just use barbed fittings and worm gear style clamps? I know there's some pressure there but I was curios at what the worm gear could take... It's the output side of the filter good thing too its only 10-12" long but I'm sure it's over the top just like everything with the badge on it.
My theory on this is that it was only firing when it could muster the pressure to open the injector then the fuel pump couldn't keep it supplied. Speed sensor will be installed just as PM hopefully find a filter later today.

Rogue_Ant

If there is two things you don't want to leak, its the brake hydraulic system, and the fuel system.
Just do it the right way, and don't worry about it.

Trav

All kinds of fuel engine is in time new speed and ref sensors. injectors fire consistant spark no leaks any where still no start. Shouldnt the injectors fire in twos? mine fire all four at the same time... is there just so little delay its undetectable? I have tach bounce. The only thing missing for verifying the basics is air.. the output on the air meter is consistant no spikes or drops. Im ready to throw this thing in the garbage :/

Rogue_Ant

The injectors all fire together - so all 4 fire at the same time.
Have you checked that the rotor isn't slipping?
Have you checked cam-timing?

Trav

the rotor did appear to be a little late on number one but of course I *** u MEd that it was keyd and wouldnt slip engineers are brilliant Ill look shouldnt it point directly at one at TDC

Trav

and yes cam is in time.