Ziff951

I'm posting all this again in this new thread and condensed a bit, since my first thread got a little stale....I figured some fresh eyes, that kinda thing couldn't hurt. Thanks for the help guys....I've read a thousand threads on 'no start', 'won't start', 'dme, no start', 'dme trouble shoot no start', sooooo frustrated...

If I'm definitely getting spark and fuel (tested half a dozen times, including starting a fire) and it won't start, just cranks and cranks... does that sound like a DME issue? I emailed with Loren at www.systemsc.com and he doesn't think it sounds like a dme issue...ugh. Then, I retested the injectors with the noid light and noticed that when I cranked it for more than 5 seconds, or so, the light seemed to fade out...what could that mean? I'll check the coil tomorrow, too...

So far:
I've jumped/tested the relay, it's good
tested/replaced DME temp sensor,
replaced speed/ref sensors,
started a small fire while testing for fuel,
have 1 bar on key turn, so KLR should be good?,
checked tdc 4 times,
and I don't have the alarm..(no second key hole, right?)

My car has LR MAF
55lbs injectors
3" exhaust
LR wastegate
mafterburner
sport turbo
blah, blah, blah..

She ran like a beast before I did the belts, pulled the intake and replaced vac lines and some electrical connections. I need help..

Stephen

LS1951

I had the same problem with one of my 944's even after installing new ref/speed sensors. As you know, many things can cause this problem. In my case it was corrosion on the wire harness. Have you checked the car side of the ref/speed sensor wires? This is the part after the plug that runs to the DME. I pealed the rubber boot back from the plug and found that the ground/shield wires were corroded. I cleaned off the corrosion and the car fired right up!

Sorry, I guess if your getting spark than you obviously aren't having a problem with your sensors/harness.

LS1951

Also, I'm sure you know about this site but just in case you don't.... check out the speed & reference sensor section in the Garage Shop Manual

http://www.clarks-garage.com/

carlege

i guess your getting tach bounce

jerome951

Here's my thought:
If you're getting spark and fuel, you should have ignition barring the following:
- timing is correct - re-check plug wires - they could have been mis-aligned on the dist when installed
- spark is sufficient to burn the gas - try swapping in another coil if you have one
- air-fuel ratio is somewhere close - try pressurizing the intake to look for a massive leak

Also to clarify, are you getting any combustion at all?

barks944

I had very similar problem and fixed it by replacing the distributor and rotor arm. I had fuel I had what looked like a good spark but a small crack in the rotor arm was stopping me from starting. I had begun to suspect diesel in the tank!

gt37vgt

just a little reminder Have your extinguisher on hand .there is pressurized fuel sparks and a angry guy pulling hoses and wires
if your spark can't jump 3/4" its too weak
start messing with some other fuel " aerostart" " tracktor smack" ""start ya bastard" propane ..
if its too rich pull the pump relay then it should start for a moment after it cranks out ..

LS1Porch

Have you tried starting with starting fluid? (I know, it's not good for the motor...but it'll narrow down your problem in about 10 seconds).

quinnfiske

The way I read this, it was running fine. Then you replaced the belts and vac lines and now it does not run at all. I would recheck every single thing you touched. Is the cam timing correct? Check to see if every vac connection is correct and in place. Has the rotor come loose inside the distributor cap? Maybe the little screw fell out.

Ziff951

Okay, great feedback, thanks everybody..
I will do another full sweep of everything again tonight. I think I need to verify that my spark is strong enough and fuel is coming out properly (my gauge reads 40psi while cranking)
I have tried
pulling the pump fuse and cranking, no go.
pulled an injector wire and tried, no go
carb cleaner in the intake, no go..(which makes me question spark again!?..not strong enough, maybe)
my rotor and cap are new, but I can switch back to the old one...screw is definitely in tight...but I'll recheck anyway
I'll try pressurizing the intake...how much psi should I set to? pretty low, I assume...
tach bounces a tiny bit 1/16", maybe? I switched in an unkown dme and the tach bounced wildly...that doesn't seem right, either...?
I'll also get into the corrosion theory again, too..the wires were pretty toasty..


I do have a .45 cal pistol...maybe if I 'vent' the hood a little bit.... ;-)
I'll update when I run some more tests. The help is much appreciated.

Stephen

400hp944

What do you mean by "bounced Wildly?" It should hop up pretty far while cranking. If memory serves me correctly, mine would hop nearly all the way around when my DME relay was bad. If your DME was only showing 1/16" of hop, that sounds to be the problem??? Unknown DME? Did you put your chips in it before you tested things? That could be why it didn't fire with the other DME in.

carlege

ARE YOU GETTING PRESSURE IN THE CYLINDER ? This might be really bad and explain why the car isnt starting. i would do a compression check and see if your even getting that. You might have had a messup while doing the belt and bent a valve?

Ziff951

Did compression and it's at about 140 across the board.

The DME that has the LR chip in it, that the car ran great on previously, only gives me a tiny little tach bounce.
The DME that the PO had in a box of 'stuff' has, what appear to be, the regular chip in it. By unknown, I meant that I have no idea what the status of it is. But, when I popped it in there, the needle bounced halfway around the tach while cranking. The thing is, I just can't remember what the tach looked like when the car was working properly before....I never really thought about it.
Maybe I'll switch the LR chips into the other DME.

Also, I read somewhere that hooking up a battery charger while the cables are still connected could fry thing. Is that possible? If so, does anyone have details on that? Would it kill the DME? or the chips? If so, would I still be getting spark and fuel?

Thanks for the brainstorming..

ausgeflippt951

Assuming the S&R sensors are doing their job, the amount of tach bounce you should be seeing will not be that much. I've personally never seen half the tach-worth (3k rpm? jesus.). It should be moving, however. If they weren't working, you wouldn't see any movement at all (ask me how I know).

I went through a no-start on my last 951 and it ended up being the DME. After trying the "shotgun parts" method, I resoldered the whole DME (yes, by hand) and voila! It fired right up and never had a problem since.

Do you KNOW the wiring harness is good? Now might be a good time to upgrade to a Lindsey fuel injector/knock sensor/S&R sensor harness. Good quality, and it'll eliminate that from your list forever.


Did you try replacing the coil? They're cheap, albeit pretty reliable...

Ziff951

Thanks for the response Collin.
I replaced the S&R sensors (and the car side clips) and
rewired the clip ends of the injectors.
The noid light says the injectors are getting a pulse (although, if I crank for more than 5 seconds or so, I think the light fades. not sure what that means)
The DME (that worked previously) only registers a little tach bounce, which seems normal.
The boost gauge shows 1 bar on accessory, which should mean the KLR is okay.
Don't know about the knock sensor..

Here's my big DME question
If the DME is bad could I still be getting spark and injector pulses? Could they be incorrect signals? I haven't been able to find a ton of info on all the various symptoms of failing DMEs.