1990 928 GT - Failure to start following rain...

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14 Aug 2012 16:48 #10106 by Cu++er
This is a new issue. The car runs great until driven in the rain, & then it won't start for roughly 5 days afterwards.

The exact symptom is: first time turn over (day after rain) tries to fire one time only, & quickly chokes out on the first puff. From that point on it only turns over and never attempts to fire or puff again (until left alone and retried again roughly 4-6 hours later, whereas it will puff once again, & then only turn over). We checked spark on both coil outputs, & both fire. However, the right one seemed just slightly less than left, & both coils are just two months old! Checked spark at all eight plugs, & all are perfect. Can smell fuel strong, and fuel pressure is 50# at rail. Checked injectors with NOID light, & have proper pulse. Pulled Mass Airflow connection and no change. Left airbox off to ensure proper air inlet, & same.

We considered reference sensors or timing, but how could rain and 5 days to dry out possibly affect that? What symptoms would a failing Reference Sensor give?

Once it dries out, it runs like a beast and never stumbles once. Have driven it for days perfectly, so long as no rain. The really strange thing is it will fire fine on the day of the rain. It just won't start the following day.

I pulled the fuse compartment cover and checked for possible water intrusion, and see none. I pulled ever single fuse and relay, & cleaned the connections with fine sand paper, but same. The ground connections all just got checked recently and cleaned, by a mechanic. I can't imagine those causing issues this quickly.

I replaced the three known problematic relays (LH, EZK, Fuel Pump), with spares I keep in stock. No change.

Anyone ever see anything like this? What am I missing?

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14 Aug 2012 21:29 #10124 by pcar928fan
Replied by pcar928fan on topic 1990 928 GT - Failure to start following rain...
Where is Wally P??? He might have an idea on this! That is VERY STRANGE!

James
78 Silver / Black-white #295
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14 Aug 2012 23:01 #10143 by 928mac
Hmmm I am going to shoot from the hip.

If you have spark and fuel it will try to fire.

But it has to be a dark blue spark or it will not fire unless lean.
You need a strong hot spark to light a rich mixture or it will flood the plug.

Moisture impedes spark at the plug and coil wires.
try this next time it happens.
remove both coil wires and spray the ends (not to much on the wire) of the wire (both ends)
Then try to start it.

Also, any of that white powder in the dist cap or rotor will collect the moisture and short the system out causing weak spark and it wont start.

Moisture in the air causing a starting problem tells me that its time for a tune-up IMHO

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15 Aug 2012 10:00 #10152 by wallyp
Several odd things about the situation.

Requirements are fuel, fire, air, compression and timing. You are losing one of these after, but not during, rain. The problem goes away with no action other than time. Tests apparently show all requirements present, despite the fact that the engine will not run...

My best guess is that you are losing spark in all eight cylinders. Unless the plugs are new, my first action would be to replace the plugs with standard copper, single electrode Bosch plugs, properly gapped.

My reasoning: The ignition system develops only enough voltage for the spark to get to ground. You want the spark to go to ground across the plug gaps, which means that the secondary insulation in the coils, coil wires, distributor caps, rotors, plug wires, plug caps, and plug insulators must be good enough to keep the voltage required to jump the gap away from ground.

Somewhere in your secondary ignition system, the voltage is going to ground instead of firing the plugs. Since your test seems to indicate that you have ample voltage available, one possibility is that the plug insulators are dirty enough that dampness allows the voltage to travel down the tip insulator instead of jumping the gap. If the plugs are worn, the tips will be rounded, which increases the required voltage. Since plugs need replacing eventually anyway, you won't really be wasting money if this doesn't fix the problem.

You basically have two independent ignition systems. One bad coil, distributor cap, or rotor button shouldn't keep the engine from starting. But - the next time that the problem occurs, remove each distributor cap and rotor. Using a good light, very carefully check for any traces of moisture on the inside or outside of each. Also look for any tiny little punctures or burn marks, cracks, dirt buildup that could hold moisture, or corrosion. Some minor corrosion on the tips of the rotor and the inner connectors is normal.

If the crank position sensor is bad, you will normally get no spark and no injection pulses.

I can think of no mechanical problem (cam timing, low compression, etc.) that is moisture-sensitive, or is self-healing.

Wally

Wally Plumley
928 Specialists
www.928gt.com

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16 Aug 2012 08:19 #10196 by Cu++er
The car just came back from getting tuned by Howard Wright at European Classics of Atlanta, who is pretty much "The Man" when it comes to 928's. He did replace the spark plugs with gapped copper Bosch plugs, as well as a slew of other new parts, and pulling and cleaning every ground connection on the car. It ran perfectly for about 4 weeks following his work, including through several rainy days. Then all of this started, out of the blue.

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16 Aug 2012 08:25 #10197 by Cu++er
Just to give you an idea on recent new parts replaced by Howard, to get it running properly (it was stumbling before):

- Replaced Spark Plugs (Bosch Copper Cores)
- Replaced all vacuum line elbows (that were visible above Intake)
- Replaced Ignition Wire Set (Beru OEM set)
- Replaced Fuel Filter (Bosch)
- Replaced Air Filter (Mahle)
- Replaced LH Relay
- Replaced Fuel Relay
- Replaced Ignition Relay
- Replaced Coolant Temp Sender
- Replaced Temp II Sender
- Replaced Fuel Pressure Regulator
- Replaced both Coils (Bosch)

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16 Aug 2012 08:27 #10198 by Cu++er
Oh yeah, forgot to mention that we also replaced...

- both Distributor Caps and Rotors

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16 Aug 2012 08:32 #10200 by Cu++er
We did notice recently that the insulation on the reference sensor plug/connection wires (directly below the rear of the passenger side fuel rail) is cracking and peeling back a few inches away from the plug itself. But it is only the outer black insulation, & not the actual wires. The wires actually look fine, with no apparent cracks. We wondered if that could be part of the issue, but have wiggled and reconnected over and over, with no change to the issue.

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16 Aug 2012 09:09 #10206 by wallyp
Howard is one of the best 928 techs alive - tell him I said hello.

Have you gone back to him and asked what the problem could be? He usually loves a challenge...

Wally Plumley
928 Specialists
www.928gt.com

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16 Aug 2012 09:23 #10207 by Cu++er
No. Unfortunately he is 100 miles away still, so I haven't been able to carry it up there.

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16 Aug 2012 09:27 #10208 by Cu++er
Just went out and turned it over for first time in about 4 days following the rain. It cranked up immediately, & purrs like a kitten. Soooooo... I just got off Weather.com, to see if I am able to drive it today. Such a shame.

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16 Aug 2012 10:04 #10212 by Cu++er
Just got off the phone with Howard, who is also somewhat stumped by the fact that it has fuel, spark and pulse at injectors, yet won't start. He thinks it has to be something that is making it run too rich, when there is moisture in the air. His reasoning for this is the fact that I told him that it smells much stronger than normal of fuel after 3 seconds of not cranking, and because we pulled one of the plugs and it was fairly saturated with fuel.

But he had no ideas on what would cause that. I wish I had a spare M/A Flow Meter to put on it, but don't. Anybody anywhere near me got one I can use to test it? That was the one component that tested out with the Hammer when at Howard's shop, yet he felt it was borderline, based on the numbers. It was sent off and re-wired last year, by a fellow that Jeannie/928 Specialists recommended to me. It ran great following getting it back from him. I wonder if it needs to be rewired again. Any thoughts on that?

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16 Aug 2012 10:05 #10213 by Cu++er
BTW Wally, Howard chuckled when I told him what you said. He likewise, spoke very highly of you.

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16 Aug 2012 15:06 #10219 by wallyp
Wet plugs can be too much fuel, or too little spark.

To test the "too much fuel" possibility, the next time that the problem happens, hold the throttle down and try to start the engine. When/if it fires and runs for a few seconds, then clears up at least partially, you have diagnosed that the problem is too much fuel. If the engine doesn't run at all, pull the fuel pump fuse, hold the throttle down and try to start the engine. If the engine then tries to run, or runs for a few seconds and dies, replace the fuse, hold the throttle down and try again. If you can get it running, you have diagnosed "way too much fuel".

If none of the above helps at all, and the engine doesn't even fire, you may have just diagnosed "no fire at the plugs" instead. That diagnosis sounds a lot less likely, after what has been done to the car.

Wally Plumley
928 Specialists
www.928gt.com

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17 Aug 2012 03:11 #10227 by 928mac
Ok kent, I would say howard covered all the tune-up basics.
You maybe on the right track at the MAF sensor, they will do strange things but I do not know if moister on the resister wire would do it.
What you can do to test that theory is whan its nice out and it starts and runs fine. shut it off, use a spray bottle and fith the air cleaner off give about 5 good sprays in and on the MAF. let it sit for 3 min and then start it. if it acts like it dose when it rains you hit the problem, if not then lets move on.

There was a comment earlier about water running down onto the (CP)central electrical panel. Make sure that moister is not getting onto the electronics that way. remove and check the LH connector for moisture of water stains is another thing to look at.

I hope you find it so look close at everything and let us know.

Brad

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28 Feb 2013 09:17 #13714 by Cu++er
Fellows, this issue continues to plague me. I could sure use some help. I have been stranded 3 times with a car that would not crank, recently. In every case, I had to just call someone to get me, & then return hours later to a car that cranked up fine.

The symptom that I think we need to focus on is this:

When the air is damp (day of rain, or day or two following rain), the car intermittently will not crank. But the really strange thing is the 'PUFFFFFF' (like a gasp) that sounds like it tries to fire only on the first attempt to turn over, & then after that it the starter only turns over and over, with no fire nor further gasps. However, you smell fuel strongly, as you attempt to continue turning it over. I have found that if I hear that PUFFF, I just need to back off attempting to start it, because it works like flooding symptoms. The longer I attempt to start it, the longer the delay before it will restart hours later.

I troubleshot it in my garage for hours, over the weekend (while it was rainy and wet outside, might I add). I thought it might be Mass/Airflow related, so I unplugged the plug from the MAF, & it still won't crank. I replaced my plugs (Bosch Standard Copper Core), and the old plugs looked fine still. I pulled both distributor caps and all is crystal clear in there, with no moisture. Wiped all down again with a dry cotton cloth, but no change after reassembly. I pulled the central fuse/relay panel and inspected all. No moisture that I can see anywhere (the car has been stuck in garage for 3+ weeks now, due to it leaving me stranded). No lines showing possible water intrusion on or around the LH connector. I pulled the (new Beru) coil wires, and checked for water intrusion/moisture; and saw none.

I am stumped!

I also want to say, once it does finally start - it runs perfectly. No hesitation, degradation in power, etc. Of course on real cold mornings it idles high (swinging up and down slightly) for a few minutes until warm, and then settles out smoothly after a few minutes. But I am figuring that is normal.

Thanks in advance for any help on this!

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28 Feb 2013 09:21 #13715 by Cu++er
Could my Fuel Injectors possibly be plugged, & pissing instead of atomizing? I could possibly see a straight stream not firing properly, & flooding things out. But why then would it fire up later, perfectly. And why would fuel injection be prone to any issues related with moisture in the air?

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28 Feb 2013 13:44 #13716 by Kiln_Red
I think you still need to isolate whether this is a fuel or ignition issue. Remove the fuel pump fuse. This also shuts down the injectors on your car. Pull the cover off of the air box and spray starting fluid onto your filter for a just a few seconds. See if the car hits on the ether. If so, then this is a fuel problem. If not, then it is an ignition problem. If you're still not sure, remove one plug wire from each distributor cap. Hook up a spare spark plug and have a helper turn the car over. Lay the plug threads over one of the bolts for the engine cross brace. Observe for spark. Do this on one wire from each distributor cap.

Report back. Also, there is a two pin plug for your ignition trigger units at the passenger footwell slightly above the CE panel. One wire is white and the other is green, so it's easy to identify. Check its condition and look for moisture traces.

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01 Mar 2013 08:02 #13722 by wallyp
If there is too much fuel for the car to start, pulling the fuel pump fuse will stop fuel delivery. When you then try to start the engine, if it tries to run for even a few seconds, you know that the problem is too much fuel. You haven't mentioned trying this...

Wally Plumley
928 Specialists
www.928gt.com

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01 Mar 2013 13:38 #13731 by Cu++er
Will do. Thanks fellows! Now I have to wait on it to rain, so it will fail again, so I can test it with your steps. Will post results afterwards.

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02 Mar 2013 15:42 #13739 by 928mac
I cant remember reading if you tested for spark when it would not start?

Have you thought of the crank sensor?

you could wiggle it and see if that changes anything or even warm/dry the sensor and wire with a hair dryer just to tray and eliminate what it is not.

The crank sensor has caused many a dead cars and it is exactly in the wrong area to get moisture.

in this picture the little round knob at the top is the bottom of the crank sensor that it pushed down through the bell-housing.
so this should help you understand that it is under the air cleaner at the very back of the motor right around that throttle cable pulley plastic wheel

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03 Mar 2013 06:31 #13753 by Cu++er
So it happened yesterday morning again. So I tried the things you fellows recommended.

First I pulled the fuel pump fuse and it made no difference. It just turns the starter over, with no fire at all. So I put the fuse back in.

Then I pulled the air box and sprayed starting fluid onto the air filter. No change. Same symptoms and no start.

About 6 hours later I went back out there, & it cranked right up. Man, I am really frustrated.

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03 Mar 2013 10:55 #13757 by Kiln_Red
Kent, it didn't even hit off the starting fluid?

Frankly, I need more info. Did you depress the gas pedal to the floor when you tried to crank it over with the fuse pulled?

Assuming there wasn't an excess amount of fuel in the engine, it is probably safe to assume that you don't have any spark. You need to remove two plug wires, one from each cap, and check for spark with the instructions I posted before.

Go to the parts store and rent a NOID light. You need to check your injector pulse simultaneously. Report back and be descriptive.

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04 Mar 2013 10:20 #13775 by Cu++er
Not at first. I let it turn over with no pedal at all. Once it did nothing, I pressed the pedal to the floor and held it. No change. I smelled fuel strongly afterwards when I opened the hood, but it could have been from before I pulled the fuse.

I have spark tester and NOID light sets. Unfortunately, working on these cars for several years has forced me to stock my toolsets pretty well. Will let you know what they show, on next failure point.

Thanks for the help Austin.

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05 Mar 2013 17:52 #13796 by Dean_Fuller
Replied by Dean_Fuller on topic 1990 928 GT - Failure to start following rain...
Are you getting a wet passenger floor board after a rain???

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05 Mar 2013 19:20 #13801 by Normy1
Have you sniffed its butt?

[sorry, I'm a pervert, and proud~]

Seriously, how do you know that it is getting too much fuel? When it won't start, have you sniffed the exhaust pipes? If it is getting too much, then it should be obvious.

For some reason, I suspect that your fuel pump is NOT working. You crank it and residual fuel makes it work for a few seconds, but then it shuts down. If your fuel pump is working, right after it refuses to start you should sniff your exhaust pipe and CLEARLY smell gasoline.

How do you know your fuel pump is working?

N!

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10 Mar 2013 15:00 #13847 by xstepson
From what I've read here, we don't know that it has fuel or spark yet, do we?

The only way to know for sure about the fuel pump is to jumper the relay.

Then, we have to know if the injectors are firing

And we need to know about the spark and if it's happening.

My bet is the spark is missing due to the water/moisture somewhere. A likely candidate, as posted previously by Brad, would be the Crank Position Sensor connector.

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16 Mar 2013 18:03 #13895 by linderpat
Replied by linderpat on topic 1990 928 GT - Failure to start following rain...
I'm in the camp with the moisture getting in somewhere. Even tho your mechanic replaced them, could be a bad set of plug wires or a crack in the distributor cap that developed afterwards, aloowing moisture in. Something has been breached. Test and very carefully inspect the new things that were replaced. If you have the old parts (cap, plug wires) put them back on and see what happens.

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23 Mar 2013 00:27 #13981 by 928mac
Verify fuel & verify spark

But

Also make sure the battery is not week!

If I have a week battery, even with booster cables from the truck on, the car will not always start or even fire (try to start)

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23 Mar 2013 11:38 #13982 by Alan
Based on your symptoms - it seem to me it must be lack of spark/adequate spark.

The most likely thing to be affected by mositure (and recover over time as it dries) is the high voltage side of the ignition.

If you have any degradation in insulation then moisture can create a bypass path that for 12v would be totally irrelevant BUT that for ignition spark voltages looks much like a low impedance short.

So this narrows it down to Coil, Coil to Dist, Dist, Dist Rotor, Plug Wires, Plugs.

What on this list hasn't been replaced? Seem you have said all - but are you really sure? - double check?

Did you replace the distributor body/cap - this is the most suspect to me since its a single point failure affecting many cylinders. BTW I think the rotor is the least suspect since its protected. Failure mechanism = hairline crack often quite invisible.

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23 Mar 2013 17:26 #13983 by xstepson
Where is the OP? He hasn't posted since 3-4-13.

I don't think he is getting spark either, but he hasn't tested to tell us that.
Actually he hasn't told us if he's getting fuel either.

I have my suspicions about the cause, but I want to know more before I post.

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