harveyf

Well, here we go. A very baffling No Start issue. The car is a 1986.5 with EZF. The previous owner (Joel Roberts) installed a Porken S300v3.5 chip.
A similar issue occurred about 2 years ago, after I had recently purchased the car. At that time it mysteriously resolved itself. The car will crank and attempt to fire but will not catch and run. Here is what I have done since the first occurrence 2 years ago.

Cleaned all grounds
Replaced negative lead at battery
Removed CEL and cleaned the CEL connections with Deoxit.
Full intake refresh. For details see here: http://newhillgarage.com/2015/07/15/...p-end-refresh/
New spark plug leads. New plugs.
Injectors cleaned by Witchhunter.
New CPS sensor and harness
New throttle position sensor harness
New fuel pressure regulator.
New fuel filter.
New Greg Brown fuel lines.

The car was driven almost weekly, sometimes on long trips, for about 6 months, without incident. This July I took major damage to a wheel and the car was parked for about 2 months. Started about every 2nd weekend. One weekend it started. The next weekend I found a dead battery. I recharged the battery (6 amps max). At that point, the car would crank, attempt to fire, but would not pick up and run. Here is what I have done since that time.

New battery. Cleaned large battery terminals and also the 2 smaller red leads at the battery.
After some false starts, I have implemented the Porsche test procedure “Test Plan EZF Ignition and LH-Jetronic Injection 84, 85, 86” using the plan for the 1986 cars.

Cleaned most of the engine compartment grounds again.
Confirmed 12V at EZF ECU plug terminal 12 (Test point 2).
Confirmed tach bounce and captured a voltage peak of about 4VDC using the peak capture on my multimeter between EZF plug terminals 7 and 19 (Test point 3).
Verified resistance for Temperature Sensor within range at EZF plug terminals 10 and 22 (Test point 5)
Verified resistance for TempII Sensor within range at EZF plug terminals 23 and ground (Test point 6) and also at LH plug terminal 2 (Test point 14)
Confirmed operation of idle switch and WOT switch at EZF plug (Test points 7 and 8).
Confirmed 12VDC to LH plug.

Took my 2 ECUs (EZF and LH) to Ken Rudd’s car and plugged them in 1 at a time. His car started right up.

I hooked up my rig to pressurize the manifold at the inlet to the MAF and listened for major leaks. None were heard.
I have a permanent fuel pressure gauge mounted at the end of the fuel rail. During all of the tests, the fuel pressure has been around 55 psi.
All the injectors that I can easily reach with a stethoscope are clicking while I crank the engine.
I verified 12VDC at one of the injector plug connections while cranking.
I check the “pulse duration” of one injection pulse. It was a little variable but in the range of 100 to 250 ms.
I pulled 2 plugs and could smell gas on the plugs.
I tested all 8 plug leads by using my timing light as a “noid”. All are firing. I removed 2 plugs (one from each bank of the EZF) and visually confirmed a spark at the electrode while cranking.
I checked timing while cranking. Approximately 10 deg BTDC
I pulled the covers on the cam pulleys. With the engine at TDC, both timing marks on the cams are spot on. The timing belt is intact.
I checked cranking vacuum at a line near the brake booster. It is about 2 psi.
I found a cracked vacuum line on the fuel pressure regulator. I replaced it. There was no gas at this vacuum connection. I have not checked the fuel dampers but suspect that if they were ruptured I would not have 55 psi fuel pressure.
Sprayed starting fluid into the intake. No effect whatsoever.
An interesting test was I clamped the fuel inlet line to reduce fuel pressure. The car seemed to like this but once it tried to run, the restriction was too much and it lost fuel pressure and died. This was predicated on trying to obtain a 38 psi fuel pressure per the WSM. Roger has since advised me that the Porken chip does indeed require the higher 55 psi fuel pressure.

I am totally out of ideas. Fuel, air, spark. The damn thing should start!

Here is a link to a Youtube video I uploaded so you can get an idea of what is (not) happening.

Cosmo Kramer

Try your MAF on a known running car. My MAF died without warning and put my S4 in limp mode (it would start but barely). The S3 doesn't have limp mode so it may not start at all with a similar fault.

harveyf

Bump for video added.

harveyf

Here's another video showing the response after I add starting fluid.
https://www.youtube.com/watch?v=CDDe...ature=youtu.be

harveyf

And here is a video that I can only guess shows that combustion by-products are being generated. Or maybe there is a new mouse nest in my rear muffler!

https://www.youtube.com/watch?v=KYrz...ature=youtu.be

Cosmo Kramer

Unplug the MAF and try starting again. Also make sure the battery is charged in the video the cranking sounds weak.

harveyf

Cosmo, I'm on it. When I get home 2 days from now. Thanks.

Mrmerlin

Before you mess with the MAF or anything else,
please install a new set of spark plugs.

NOTE install the throttle quadrant before starting

NOTE do not start the car unless you can drive it for more than 10 miles.

What happens with the injection systems with these cars is that they will load the plugs,
once this happens the plugs are fouled.

NOTE this issue is more pronounced with the Porken chip addition,
BUT it will also occur with the stock chips.

This is a common problem with engines that are started and run for a short while,
BUT infact the car isnt driven or just moved into the garage and not given a chance to fully warm up to and stay at operating temperature for 20 mins or more.

AO

I think this is the key. It's clear you have fuel it could be too much, but it doesn't sound like it if starter fluid didn't get it going. I think the issue is either spark or compression. (We'll assume you have air).

You didn't mention if you tested/swapped/jumpered relays. Did you?

I would take one of your old spark plugs, pull one of the plug leads and ground the plug to see how strong the spark is. I think you can pull #1 or #5 without much trouble. Maybe try both to see if there is a difference from side to side.

Also, is this a 5-speed or auto?

harveyf

First, thanks for the input.
MMerlin: The weekend before I started the car and let it idle for 5-10 minutes. The next weekend the problem arose. Since I'm at wits end, I'll pull all the plugs (new this June) and clean them off. As I recall, the 2 I did pull (see below) were not sooty. I have the throttle quadrant removed so I could get a good view of the timing marks. I'm not sure why it needs to be connected since I never have to depress the pedal to get the car to start. The original problem presented with the throttle quadrant in place. By the time I shot the video, it had been removed. Even disconnected, I have confirmed that the idle cutout switch is engaged. Whatever, I like your idea about the plugs as there has now been a substantial amount of time spent under cranking with no run time. I'm also going to change the oil when this is resolved.
AO: All relays have been swapped and more importantly I have confirmed the correct voltages downstream of the relays at the various ECU pins, etc. I have request a new set of relays from Roger to install, just in case.
I did pull 2 plugs, one from each EZF bank, attached them to ground, and observed the spark. I've been working on cars for 45 years and to my eyes there was nothing wrong with the strength of the spark. But that is subjective. I did "noid" test all the spark plug leads, in addition to the 2 plugs I pulled. There was a gas smell on the 2 plugs I pulled and combined with the starting fluid check and the fact that I can hear the injectors, I think it is getting fuel.
No reason to suspect compression, based on my testing.

I've been trying to think of what could fail over a week. I'm going to check the MAF per the workshop manual (power, resistance). I'm also going to confirm "puff" coming out of the exhaust while cranking, on the off chance that rodents got in there and built a substantial nest.

I won't be back home from business until the weekend so am trying to line up my next plan of attack so all comments are truely appreciated.

Mrmerlin

Harvey sir, you can keep trying to fix it till its broken.

OR install a NEW set of spark plugs, NOT cleaned ones..

Please try Bosch silver tipped plugs part # 7900= WR7DC at Autozone ,
they cost about 1.99 each,
the least expensive but best working plugs for the 928 that Bosch makes.

If your using a colder heat range then dont use these. then IIRC its #7902 WR5DC

NOTE Install the throttle quadrant so you can go drive the car after you start the engine,

or you will be in the same boat after you shut the engine off after it has run for a few mins,
so you can install the throttle quadrant so you can go drive the car.

NOTE Spark plugs foul then can not fire properly even if you have cleaned them.

NOTE Please reread post 8 a few times to gather the info it contains

NOTE unless you have a half gallon of gas in your crankcase,
normal driving for 30 miles will remove any gas from the oil,
and it wont cause any damage to the bearings.
So just drive the car it will be OK and you wont need to swap in another 9 Qts of oil or filter

NOTE aircraft use a fuel dilution system to thin the oil during cold weather operations

harveyf

My No Start issue has been resolved, sort of. Last weekend I went out and tried to start the car. It fired right up. The frustrating part is I don't really know why.
I last attempted to start the car, with no luck, 2 weekends previous. I left for a 2 week trip with the car as I left it, in the garage. My only clue is that it was on a battery tender, so the battery was well and truly charged when I successfully started it last weekend.
Based on Mr. Merlin's advice, I left the engine running for 10 minutes at 3000 rpm. It was not roadworthy but I confirmed that this brought it up to full temp. After the 10 minute run, I shut it down and made 2 successful, immediate restarts. I then left it to idle for another 10 minutes and then shut it down for good.
These faults that come and go annoy me. Maybe it was a low battery. Maybe the plugs were fouled but I don't see how they unfouled themselves. There was a change in the weather in the 2 days before the car started (a low pressure cold front moving through, record rainfalls). I just don't know.
Whatever, this episode has motivated me to rebuild the engine FI wiring harness, as soon as I get done with the interior upholstery work.

jej3

I believe Mr. Merlin advised "NOTE do not start the car unless you can drive it for more than 10 miles."

I am not all that informed in these scenarios but I did in the past have my 90 S4 fight to come back to life after a 2 month hiatus outside of the garage. MAF and LH both died due to what I believe was my being impetuous and jump-starting.

In my view, driving 10 miles and running the RPM at 3K for 10 minutes are a bit different. The 10 minutes of driving gives you idle fluctuation and varied demands on the fuel delivery. I believe that is the most "modest" exercise these cars need vs revving at 3K.

No expert here but these cars are a bit needy when neglected.

Good Luck!

John Speake

I hope you made a mistake with this measurement.... the pulse length you quote is much too long. You should measure the time the 12v at the LH is pulled low.

Even with a cold engine I would expect the cranking pulse width to be more like 6-7mS.