Completely stumped....fuel?spark?electronics?
03-12-2005, 12:03 AM
#17
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Stan has a good point. All of the sensors should be tested at the plug for the DME as well as directly. There is a possibilty of broken wires in the loom. Sometimes at the DME plug. The temp sensors do not require voltage they are a resistance item. A good ground to the chassis from the engine is critical.
Check the throttle switch. Make sure you can hear it click as the butterfly seats. Also take a look at the bleed valve. May be backed out or even missing. If it turns easily then you might want to replace it's o-ring.
Check the intake to see that it is sealed to the head. I've had to use double gaskets is some cases where the manifold has warped. Get a diagram and check all of the vacuum hose connections. Might have cracks or be loose.
The brake booster may be leaking. Or the large vacuum lines to it.
Check the throttle switch. Make sure you can hear it click as the butterfly seats. Also take a look at the bleed valve. May be backed out or even missing. If it turns easily then you might want to replace it's o-ring.
Check the intake to see that it is sealed to the head. I've had to use double gaskets is some cases where the manifold has warped. Get a diagram and check all of the vacuum hose connections. Might have cracks or be loose.
The brake booster may be leaking. Or the large vacuum lines to it.
03-13-2005, 10:33 PM
#19
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Still not having much luck...
An update...
I decided to try a few other simple things this weekend to narrow down this problem. I'm working on borrowing a DME from one of the local guys, and crossing my fingers that this is the source of the no-start. I went ahead and drained the fuel tank and replaced it with fresh gas just to be sure. I also popped in a new fuel filter and new plugs I had on the shelf. I will plan to order a new coil, cap, and rotor to tune up the ignition, although I don't think this is the main problem.
None of these things got the car running, but I did notice that now there is the slightest fraction-of-a-second sputter after the first full crank revolution after I turn the key. This is not to be confused with "firing", but for a mere blink it makes you think. It does not repeat the "sputter" if you hold the key for several seconds, but it will do the same thing on the first revolution each time you turn the key.
I ran the car again after getting it going on ether, and as mentioned it coughs along horribly as if one or more cylinders are mis-firing and any throttle petal kills it.....until warmed up. Once it is warmed up, however, I realized that it does seem to "stumble" just a bit if you give it throttle quickly. It will rev, but that first jump in RPM's is a little rougher than I seem to remember it being.
LorenFB said - "A solution requires focusing on the fuel function of the starting process, i.e. extra fuel makes for a good cold start. Using the cold start injector as with the ether should also make for a good start. Bypass the thermo-time switch, so that the valve sprays whenever cranking. This should yield the same results as the ether."
What do you mean by the "cold start injector" and the "thermo-time switch"? I thought only the early 924's had something like a cold start injector? My understanding was that the 944 DME (early car anyway) had an enrichment curve that increased the fuel to the main injectors based on inputs from both the block temp sensor, and the AFM air temp sensor. It makes sense to me that my car does not seem to be getting enough fuel at start up and the ether compensates for that.....but I'm not aware of a cold start injector? I will try to find an injector light to verify the cold enrichment test you mentioned. This is just a "noid light" correct......anybody know if this can be found at Advance/PepBoys, or should I order the usual GM/Ford/Bosch kit for $20-30?
Sorry for the long ramble, I just want to get this problem figured out. My hopes are on the DME and hopefully I can get that tested soon. I sincerely appreciate all of the input, and I hope the conbined thoughts can help me get to the bottom of this.
Thanks!!!
Andy
I decided to try a few other simple things this weekend to narrow down this problem. I'm working on borrowing a DME from one of the local guys, and crossing my fingers that this is the source of the no-start. I went ahead and drained the fuel tank and replaced it with fresh gas just to be sure. I also popped in a new fuel filter and new plugs I had on the shelf. I will plan to order a new coil, cap, and rotor to tune up the ignition, although I don't think this is the main problem.
None of these things got the car running, but I did notice that now there is the slightest fraction-of-a-second sputter after the first full crank revolution after I turn the key. This is not to be confused with "firing", but for a mere blink it makes you think. It does not repeat the "sputter" if you hold the key for several seconds, but it will do the same thing on the first revolution each time you turn the key.
I ran the car again after getting it going on ether, and as mentioned it coughs along horribly as if one or more cylinders are mis-firing and any throttle petal kills it.....until warmed up. Once it is warmed up, however, I realized that it does seem to "stumble" just a bit if you give it throttle quickly. It will rev, but that first jump in RPM's is a little rougher than I seem to remember it being.
LorenFB said - "A solution requires focusing on the fuel function of the starting process, i.e. extra fuel makes for a good cold start. Using the cold start injector as with the ether should also make for a good start. Bypass the thermo-time switch, so that the valve sprays whenever cranking. This should yield the same results as the ether."
What do you mean by the "cold start injector" and the "thermo-time switch"? I thought only the early 924's had something like a cold start injector? My understanding was that the 944 DME (early car anyway) had an enrichment curve that increased the fuel to the main injectors based on inputs from both the block temp sensor, and the AFM air temp sensor. It makes sense to me that my car does not seem to be getting enough fuel at start up and the ether compensates for that.....but I'm not aware of a cold start injector? I will try to find an injector light to verify the cold enrichment test you mentioned. This is just a "noid light" correct......anybody know if this can be found at Advance/PepBoys, or should I order the usual GM/Ford/Bosch kit for $20-30?
Sorry for the long ramble, I just want to get this problem figured out. My hopes are on the DME and hopefully I can get that tested soon. I sincerely appreciate all of the input, and I hope the conbined thoughts can help me get to the bottom of this.
Thanks!!!
Andy
03-14-2005, 03:45 AM
#20
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Andy, do try out the DME swap!
I feel your pain with this! BTDT. It may not be the right time yet, but, sometimes, when diagnosing something like this, one must just stop........and say to themselfs......."am I 100% sure I did, and checked things like I said,and thought I did?" It happens sometimes, that we can overlook something that we THOUGHT we may have previously eliminated as a problem. I wish you the best on this problem, and can't really offer anything more, but the thought that, it just might be time to go back and start from step one again, and double check........just in case. This time with even more attention paid to even more of the details. Don't ask me why I said this.
I feel your pain with this! BTDT. It may not be the right time yet, but, sometimes, when diagnosing something like this, one must just stop........and say to themselfs......."am I 100% sure I did, and checked things like I said,and thought I did?" It happens sometimes, that we can overlook something that we THOUGHT we may have previously eliminated as a problem. I wish you the best on this problem, and can't really offer anything more, but the thought that, it just might be time to go back and start from step one again, and double check........just in case. This time with even more attention paid to even more of the details. Don't ask me why I said this.
