Zirconocene

Thanks Gary,

Agreed. I went through and figured out how to bypass the alarm on my '90, only to find that it was not the alarm system. I was so certain that was the issue (sad trombone noise). The start Mike and I made on the other, more typical checks all passed. We weren't able to do some of the oscilloscope work that is called for, but the voltage and continuity tests were all looking nominal. We didn't finish out the test schedule, however, so there may yet be something at the end of the list that might be tripping things up. However, as Kevin points out, there is the hint of a start, so it sounds like I'm in an atypical situation.

Cheers

Kevin in Atlanta

Two times that has happened. Once, when I swapped the TPS and CPS connectors. Once, when I moved my car about 10 feet. The former does not match your situation. The latter cured itself a couple of weeks later.

Divine intervention? Who knows but I no longer start and stop my 90's engine. Always let it warm up a bit.

Both of the cars in question are 90 S4s. Coincidence?

Michael Benno

@Zirconocene

• CPS tests require an oscilloscope. So it's best to swap it out. I have small hands and can help you with swapping it out.
• TPS we can test that ourselves with a DMM.

Jason89s4

Did you try the starting fluid per Merlin's suggestion? Mine too--process of elimination. Its five dollars, not half day pulling parts
CPS_Is the tach "jumping" when you crank it?
Your post #7 and other comments sure do smell like alarm issue. I know you said it was bypasseed but there is a lot more to the alarm system than one may think.
Again, process of simple eliminations....see Gary's post #15k.

Better yet, dont do any more and sell me the car!
Jason

Zirconocene

@Jason89s4 : I'm going to dive back in this weekend, other projects consumed me for a little bit. I'm going to start with pulling vacuum lines to smell for fuel, check pressure, etc. I know the pump works, or at least makes normal sounds, but a pressure check will help identify if there's an issue there.

As to your last point, Ha! I love this car too much, even in its degraded state, to even think about it. It will be back to good, one day...

Cheers

Jason89s4

But do you have spark?
Squirt of starter fluid will tell you.
Test the current to the injectors.
( not to sound like a broken record ….reset the alarm. All sounds like alarm)

Don’t just assume that because your fuel pump is running and you have good pressure, that the gas is actually MAKING IT TO THE COMBUSTION CHAMBER! All could be good but your injectors or fuel lines are clogged. Been there done that.
Squirt of starter fluid will tell you!
(your fuel system may not be injecting fluid into combustion chamber….but starter fluid will)
if starter fluid does nothing then you don’t have spark. Simple. And it all starts with a simple test.

Mrmerlin

Thank you Jason

928 GT R

If it cranks a bit and then stops, could it be a partially flooded cylinder from a failed head gasket?

Hydrolock?

Zirconocene

@Jason89s4 : Sorry, I don't mean to make it seem like I'm ignoring the suggestion about starter fluid; I've just never done it and need to figure out how to make that happen. It's a good idea, just not part of my current wrenching experience.

@928 GT R : I have never hoped more that someone is wrong but I'd be lying if something catastrophic like this wasn't somewhere in the back of my mind.

Testing will continue today.

Cheers

Jason89s4

Preparation:
tools needed: none
supplies needed: can of starter fluid available at any car parts store. Shop rag to clean your hands.
Steps:
1. Take off air filter housing top only. (Four straps)
2. Remove air filter. Set aside to a clean dry spot.
3. Spray 3 second of fluid into Mass Air Flow entrance below the removed filter.
4. Try to start car and see if it will start better for a few seconds. (If you have a partner doing little small squirts while you start it and work the gas pedal, you can actually run it until the can runs out!)
5. Report results and heed the advice. (No offense guys, but things like ‘I think your motor is blown’ is not advice. )

If that exceeds your wrenching skillls, I suggest you have it towed to a mechanic.

Zirconocene

Thanks Jason, I can do that. I had a vague notion that it was a 2 person job, so that process you laid out is very helpful.

I verified this morning that I have fuel pressure at the rail test point, though it falls to about 5 psi over 30 - 45 minutes.

I'll go get some starter fluid and see what I can see.

Thanks again

Zirconocene

A few data points from some testing today;

- Fuel pressure is good when I jumper the relay and activate the pump with a momentary switch. The pressure doesn't stay high for very long; immediately after I let go of the switch it drops from 50+ psi to about 40-45, then down to less than 10 over about a half hour.
- I hooked up a MityVac to the vacuum line that goes to my fuel regulator and rear damper. I am not able to pull any vacuum whatsoever.
- I looked around for disconnected hoses but there was not anything particularly obvious, though the data point above says there is likely something wrong somewhere. Right?

A funny electrical thing just as I was buttoning things up for the night:

- I noted today that my passenger window is not working any longer. This is new, but may be unrelated. Below is what's weird.
- Both doors are unlocked to start.
- On trying to lock the car from the driver side, the lock goes down but immediately comes back up.
- I went to the passenger side to lock the car and on doing that, the alarm began.
- I unlocked the passenger door, that stopped the alarm.
- I locked the passenger side door, and everything locked as normal.

I bought the starter fluid and can run that test tomorrow but it seems like there are a few things going on here.

Separately and also of concern, there is moisture around and on my central electrical panel, so I need to get that taken care of. I investigated the drain flap but from what I could feel with my hand wedged down there it doesn't seem like it's clogged. I'm a little afraid I need to remove the blower and do some serious seal refreshing and water entry mitigation.

Thanks

Mrmerlin

Best bet drop the CE panel, put a towel over it,
Then remove the 3 bolts for the fan motor,
then drop the blower box,
the fan will drop down out of the blower box hole.
the towel will catch all the junk inside the blower well. then remove every relay ,
see if any are filled with water ,
use D100 on all the connections.
Reseal the blower box with 3M strip caulk found at the auto body store.

Jason89s4

Fuel pressure drop is a symptom of bad FPR. Shop manual has specs for how long system should hold decent pressure when off. .and dropping down to 10 psi quickly is not within spec. (Put it this way, the system is designed to hold enough pressure overnight and then start right up in the morning)

Michael Benno

Glen:
Regarding your fuel pressure tests, The manual states:

• Pressure when fuel pump running (engine off) the pressure should be 3.8bar (55psi) +- 0.2bar (3psi). Your test value of 50psi is below the specification.
• Pressure after 20min with fuel pump off the pressure should be 3 bar (50psi). Your test value of 10psi is way below the test specification.

I agree with @Jason89s4 there is something wrong with your fuel pressure system. Potentially your aftermarket FPR (Radium). Please test the vacuum port on the FPR. Does it hold a vacuum? If not that is a problem. If the FPR holds a vacuum then keep chasing vacuum leaks in that system.