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Helping Bill here in Vegas sort out an issue. Need some collective wisdom from you all.
No start on an 87 S4 auto.
Cranks fine but no indication at all that the engine is going to even ignite..start etc.
Car ran and started perfectly fine until it didn’t. (don’t they all!!) Only indication prior was a slight stumble a few moments before it being shut off (it didnt die) . It subsequently will not start and is where we are at now.
Whats has been done….
LH and EZK have been swapped from a known good running car.
All pertinent relays have either been swapped…jumped etc. Pertinent Fuses checked
Engine ground point seems good and as a back up we took a set of jumper leads and grounded the block to the “body” manually. Yes we are desperate!
Installed a brand new battery.
The fuel injectors appear to be functioning. 1) we smell gas 2) I can feel them pulsing with my figure on them and 3) a small test LED I made on the injector lead shows they are getting a signal.
With the fuel pump relay jumped the fuel pumps runs
SO………..In a nut shell. We appear to have FUEL.
The issue we are leaning to is ignition….but WHAT??
EZK swaped for a known good one. As with the relays.
The tach needle moves when the engine is cranked.
Both final stage ignition modules have been swapped for known good ones.
Both cap and rotors removed and cleaned…and no cracks or moisture apparent.
NOW THIS IS WHERE IT GETS BIZZARE… and totally baffles both of us.
We have hooked up an induction timing light on the main coil wires to the rotors..... and from the rotors to each spark plug lead. The results are odd….
On the PAX SIDE..With the inductive clamp on the wire that feeds the rotor from the coil we get “a flashing timing light”…that’s good
On the DRIVER SIDE..With the inductive clamp on the wire that feeds the rotor from the coil we get “a flashing timing light”…that’s good
Now the problem is when we test each individual lead from the respective distributor/rotor to the spark plug.
Stay with me here….
On the passenger side (US) the only wire that gives us a “working/pulsing ” timing light (ie..Inductive signal), is cylinder # 4…all others on that side.3..2..1 do not.
On the DRIVER side (US) the only wire that gives us a “working/pulsing ” timing light" (ie..Inductive signal) is cylinder #8 …all others on that side.5,6,7 do not.
We are both at wits end with it.
Any one shed any light on the function of the coils..how they fire… the distribution of the spark voltage? Etc etc….we will follow any lead (no pun intended)..but I don’t see how it can be the spark plug leads or the plugs . Too specific of a failure point on each side to random
Thanks guys.
pic is words 1000 words. GREEN works.....RED doesnt.
I wouldn't rely in the inductive results. Pull all 8 plugs, put them on the plug leads, set them on the head and verify visually for spark at each plug.
If yes, put all plugs back in. Crank with carb cleaners spritz into the intake, and feather the throttle. Report results.
If no, or only two show spark, test EZK and LH sequentially in a running car. Report results.
We had a pump that ran, but no pressure at the rail. Gunk and dead int pump in the tank.
put the LH from the non running car into the running car see if it runs, not the other way around.
Post a picture of the CE panel.
Pull the coil wires off of each coil and cap and inspect the ends for green corrosion
then put these coil wires into the running car one at a time.
put both of them(LH and EZK) in my car..it started and ran.
will look at the coil wires them self. But both sides...at the same time go out? will check them anyway. The other bank does the exact same thing as in the video...except its only #5 that appears to have voltage in the wire(timing light flashes).
To get spark from only one spark plug wire means the rotors are not turning.
Broken timing belt.
i guess we never thought to look at the worse case scenario. That does make sense....but...wont a belt failure be more of a catastrophic SOUNDING event? or does the motor just die in an unspectacular quiet fashion? I do recall looking in the vent hole on the cover, i didn't notice anything odd...but then i really wasn't looking specifically for a bad belt. A belt was there and ....ugh......perhaps just laying on the cam sprocket. now feeling a bit nauseated.
Had the exact failure on my GT back during one of our track days. It stripped all the teeth at the crank... We cranked the engine numerous times with similar results (spark detected on one wire but not others).
I only lost two valves (I think they were exhaust on #4). They were only very slightly bent. I think if we didn't crank it so much to try and get it started, I may have gotten away with no bent valves.
Good luck..keeping fingers crossed for you.
02-22-2019, 09:57 PM
87 S4 not start...baffled beyond belief.
