No Start and I'm stumped

[Freaky]

I'm a new guy to this forum, and everyone says you guys are a lot of help, guess I haven't been here long enough for the "turbo guys" to consider worthy. I tried posting this on the 944 turbo page, but got no help, other than one guy asking if my rotor was loose.

I have an 1987 944 turbo that died the other day...I pulled into traffic, went into boost, hit the rev limiter. The car ran fine, but when I stopped at a traffic light, it began to run rough, miss and got a little backfiring. Shut down the engine, looked for any obvious problems and found none. When I tried to restart the car, I got nothing. AAA to the rescue. I have a few friends with 944 turbos here, so we started swapping things out of running cars to see if we could find the problem.

I have tried the DME, DME relay, distributor cap and rotor, KLR, removed the MAF and chip and installed the AFM and stock chip, installed a known good coil and wire, jumped terminals 87, 87b and 30 on the relay panel (got fuel pump noise), checked fuel pressure, checked the idle control valve, checked fuel pressure (39psi).

The only question I got on my previous post was about the tach needle bouncing, with no explanation. When I turn the ignition key, the tach needle will bounce, just like the rest of the gauges, but it does not move when cranking.

Spark is low to non-existent.

The car is an 87 944 turbo with a kokeln turbo and a vitesse maf.

My eternal thanks to anyone who helps!

[Ga 951]

No tach needle bounce is indicative of a speed or reference sensor issue. Clark's garage has a good troubleshoot and installation guide.

This old post may be of help (I bookedmarked it !)

at wits end...

good luck

[Pete R]

I had a very similar problem my last track day. I actually blew an intercooler hose off. It came off just a little and was tough to see. I'd make sure all your vacuum and boost lines are ok

[TrailRider]

Definitely sounds like speed / reference sensors.

A couple of months ago I figured out my own no start condition (lack of spark with no tach bounce) was due to a loose wire at the factory alarm module.

Here is my post -

no-start condition - 86 944t

This video may help in testing the sensors -

How To Test RPM & TDC Sensors in 944 and 911 3.2 Carrera Porsches - YouTube

[Ky914Newbie]

I also want to add the tach bounce should be very slight. About 1/16 of an inch.

[rick13]

Hey "Mr. No Spark"!... Pop the distributor cap...how does the rotor look?

[Freaky]

Intercooler and vacuum are all connected and in good shape, alarm has been removed and there is a factory jumper in place of the alarm module. Speed and reference sensors were replaced with known good (we pulled them from a friends running car) and the gap was reset per clarks garage instructions.

The tach needle sits rock still during cranking, just the one bounce when I first turn the key to the run position.

Rick, cap and rotor are in excellent (new) condition.

Thanks guys, I'm sure I will be able to figure this out with your help!

[rick13]

Hmmm...

[rick13]

No bounce...definately speed or reference sensor related...weird. Maybe you mixed 'em up???

[rick13]

I just re-read your post..."Spark is low-to non-existent". So you have some spark?

[Freaky]

nope, car was running, boosted, hit rev limiter and engine ran a bit rough, I shut it down and it would not restart. It's beginning to look more like a bad ignition switch or DME/KLR related.

Turns out that the DME we tried the other day was a "spare" that was pulled from a friends car because it wouldn't always work. We are going to try the one that's in his car now this evening.

I have a few more things to test before that, hopefully it isn't my DME or KLR or both....they are expensive....and this is my only transportation except for my bicycle or public transportation.

Rick, I initially got a very weak spark, weak enough that I barely felt it when I accidentally touched the test probe while cranking the engine...A test light shows no pulse at the fuel injectors.

[rick13]

Yeah ok, Lol. Good Luck

Be sure to let us know you're findings.

Smith out.

[Freaky]

I talked to a guy by the name of Tony Callas (Callas Rennsport), and he recommended these guys for DME repair....prices for their REBUILT DME's are the same as everyone here seems to be asking for their used DME's. $275 REBUILT with a 5 YEAR WARRANTY and FREE SHIPPING.

Specialized ECU Repair, Replacement, & Testing - Restore or Exchange your Electronic Control Unit (ECU)

After a few more checks this evening, I may be calling them on Monday!

[Pete R]

Can you find a known good one to swap and test first?

[Freaky]

I'll be doing that this weekend, taking one from a friends running car. But, I may have found the problem. I tested both the speed and reference sensors using the method found on cCarks garage, and the method on ecudoctors.com website. I find the sensors within range via Clarks, but testing at the DME plug, I find 0.02v (should read more then one volt) at the speed sensor, and 0.0v (should read less than one volt) at the reference sensor. Looks like the fault is in the ignition switch.

Just waiting for verification that my understand of the readings is correct.

[TrailRider]

Have you checked out your timing belt? Since it started on after you got on it... Anyway, if the ignition possibly doesn't work out...

[Freaky]

Timing and timing belt were the first things we checked...just tried another set of speed and reference sensors....still showing 0.02 volts while cranking, so the DME isn't "seeing" the signal. But before I buy the ignition switch, I will still swap in a known good DME tomorrow.

[guru944]

Freaky:

Check your Engine Harness Grounds. See some the other "No starting" post or do a search. I have posted some remedy's that may work for your pending situation..
PM me if needed....

Later...

[Freaky]

Ok, Here's were I stand on my no start turbo; we first checked the timing and balance belts to make sure they didn't break, then we verified that the timing had not jumped. After that I began testing and checking. All wires and vacuum lines are in good shape and connected, grounds are all cleaned, battery has a charge of 13.1v, tried a known good KLR (waiting on a friend to come by with his DME to swap in). Cleaned the connections to the TPS, ISV and AFM/MAF. Swapped the MAF chipset with the AFM chipset, hooked up the AFM, still no start, tested MAF per Vitesse instructions, MAF functioning.

At this point it was determined that I had no spark, so I began some additional checks:

12v between pins 1 & 18 on DME plug....0.07v (ignition pulse to coil) FAIL
12v at pin 30 DME RELAY socket...12.02v (fuel pump power) pass
12v at pin 86 DME RELAY socket...12.11v (primary coil voltage) pass
Jump pins 30/87/87B...fuel pump works pass
12v at Coil positive, a bit low at 11.73v acceptable
12v at Coil negative...0.06v FAIL
Coil primary resistance between .4 to .6 ohms...tested 1.5 ohms FAIL
Coil secondary resistance between 5000 and 7200 ohms....5980 ohms pass
NOID light for injector pulse......NO PULSE FAIL
Speed sensor air gap reset to 0.8mm
Speed sensor resistance between pins 8 & 27 (600-1600) tested 883 pass
Speed sensor resistance between pins 8 & 23 GREATER than 1M ohms pass
Speed sensor voltage pins 8 & 27 GREATER than 1v...tested 1.3v pass
Reference sensor resistance between pins 25 & 26 (600-1600) tested 994 pass
Reference sensor resistance between pins 25 & 78 GREATER than 1M ohms pass
Reference sensor voltage pins 25 & 26 less than 1v...tested 0.01v pass
Tach Needle bounce when cranking....no bounce FAIL

I am going to hold off on checking for 12v (start signal) between pin 50 on the ignition switch and pin 4 on the DME plug until after I check with the known good DME.

I thinking that the Ignition Switch is most likely the culprit, as all the FAILED reading are in the primary start signal circuit, and the ref/spd sensor voltage readings are taken with the DME removed.

Any tests that I missed?

[kdjones2000]

Did you either jump out or replace your DME relay? I don't see that on the list.

Other than that I think you are on the right track.