Don '85S3

My '85 has an intermittent starting problem that is driving me crazy. It always starts first thing in the morning, after sitting overnight. Every once in a while, the car won't start after driving. This occurs sometimes as soon as starting it for the first drive of the day, driving about 2 minutes to the gas station, fuel up, and won't start. The car hasn't had enough driving time to get warm yet. I have jumped the fuel pump relay when this occurs, and it runs normally. The car will not start unless it sits for about an hour or so. Sometimes it seems if flooring the gas pedal when cranking over will help it start, other times flooring it does nothing. Thanks much for your suggestions!

docmirror

Well let's have a try. We need three things to start the car. Compression, properly timed spark, and a stoich fuel air mixture. If I read my print right, the injectors get their fixed 12V from the fuel pump relay. Hmmmm, I never knew that on an 85. So, one side of the injectors is powered by the fuel pump relay, and the other is fired negatively from pin 13 of the LH. Also, I see that the idle speed regulator functions on the 5-8 bank from pins 10 and 23.

I'm guessing here, that we have good spark, properly timed. since it's intermittent, that's gonna be hard to determine if that's true. I think, but could be wrong that the only thing the EZF needs is the reference timing mark from the crank pos sensor and the temp two sensor.

Test for spark: Take two spare plugs on the next drive. If the failure occurs, pull the plug wires from both front plugs (1 and 5), and connect them to the spare plugs. Set the plugs on the cam cover, and test by cranking and look for a blue spark on both plugs.

Test for fuel is going to be more difficult. If you have a multimeter it will help. If the failure occurs, you will need to check for a constant 12V on both wires to the injectors with the key on, and then pulsing on one set of wires during the cranking of the engine. Without an Oscilloscope, this is a problem.

Potential failure points: Fuel pump relay, LH relay, crank position sensor, temp two sensor, idle speed regulator, LH or EZF. The relay can be swapped with other relays with the same part number. You can swap a working LH into your car and test again, same with EZF. I believe the 86 is the same, up to VIN 999.

sjfarbs

You say that it fires first thing every morning.
But then after driving even just a mile or two, shutting down (i.e. getting gas) no go when trying to start again, then after an hour, it is fine..............

I would start testing your sensors TEMP II would be my first suggestion............

From the way I read your post, the no start is happening only after the engine temp has changed (getting hotter). Once it cools down, the engine will start on the first attempt, that suggest that a sensor malfunction.

Grab you multi-meter and head to the garage and start testing. You will find the values in the WSM 24-17.

Good luck, keep us posted............especially when you nail it!

Shawn

Mrmerlin

JB.......... Relay , Relay Relay, buy 4 of them Oh 53 is the number

docmirror

Ugh, covered that. Said that too.

Don '85S3

Thanks guys for the suggestions!

I have replaced all relays in question (long ago) and still get the problem. I also have jumped the fuel pump relay when the no start condition occurres, and the fuel pump hums along fine. I replaced the temp two sensor about 4 years ago. I haven't measured it's resistance, but would assume it should be still in good shape. I'll give the spark plug test a try next to eliminate the high voltage question.

It would be easiest to solve if it just didn't start, and stayed that way. It happens so seldom that it's tough to deal with.

docmirror

More info, cool. Ok, try to find someone that can swap LH and EZF with. Maybe Roger will loan you a pair for a bit?

Here's another thought. I've seen the ignition switch cause symptoms just like this. It'll crank all day, but the spark isn't there. Then after the third or fourth try, the contacts finally mate and it goes. The spark plug test can be useful here.

SeanR

Funny thing happened when Doc and I went to go pick up a car 2 days ago.

It wouldn't start until you stuck some foot in the gas. My 1st thought was "filter, clog".

He looks at me funny and says "it has gas, it's a metering issue"

I put a MAF on the car and it runs fine............

Moral, listen to Doc, he seems to know his **** when it comes to AFM. Just don't ask him to label a damn bolt when he takes it out of it's hole.

wag

This is a long shot, but I have an 85 with a very similar issue. Check the batter ground at the battery, and the nut off the negative side. Mine was so badly corroded it was not making contact from the brain. When you do find out what it is, please post what you found too to help us out on this.

Larry Velk

My '86.0 just went 'teats up', in the shop, thank goodness (no tow!). No spark but there is 11.some volts at the coils and the dash lights work. It cranks fine and fired a few shots before going completely dead. It also seems like no fuel either (plug was dry, no fuel smell). While I fancy myself pretty good at repair (10 years in Chevy service back in the points/condensor era) I can't read the Porsche wiring diagrams - I have the WSM. Very little info on the '85/'86 system anyway. It may be a relay daisy chain that requires current to travel a strange path to power up the computers. I bench checked the 3 relays but stupidly put them back before checking the through put so I still need to check if the points resistance is too high or not at near 0. The relay I did through check had only 0.3 Ohms accross the points with the coil engaged by 8.0 volts from a defective Makita drill battery. The relay coil resistance was around 80 Ohms on all. I need to check if I have 12 v at the relay engage slots in the board, but I can't figure out where the 12 v would come from if it wasn't there! Does an "'Merican version" of those stupid diagrams exist?
BTW, I just disconnected the alarm by jumping the 85/15 sockets and removing the module as advised. I have no jumpers at the footwell board.

SteveG

Larry: I don't think 11V at the coil is enough. You prob know a battery can show 12.4V and have weak cranking amps. Grounds: There are at least two grounds in the eng bay besides the obv batt +/-. The new visitor thread, a post by WallyP has a comprehensive list together with WSM diagram. There is a braided wire between eng and passenger side of eng bay. Check grounds on both coils and any other brown wire to chassis you can find.

Larry Velk

The WSM gives a pretty wide spec on voltage at the coil. Something to the effect that it shouldn't be a drop of more than 2 v vis-vis the jump terminal, in any case, they run on less in coil systems with resistors, I'm not concerned about the coil volts. I see I should have the terminal 30's powered up from the battery for 2 of the suspect relays, but I don't know how the plugs and wires are numbered other than A through P, or whatever. I don't have the diagram here at the computer, but I think it was a terminal 11 and 12 in a plug that I think is toward the lower right (end of alphabet). I see a thick red wire there that, it seems, should have a full 12 v even with the ignition off. My wife made hard copies of my Jim M. CD's, but maybe missed the plug info as I can't find it.
I've spent hours in search mode and few have posted resolutions of these no-start problems. A few solved with the relay deal (many more have replaced relays to no avail), one found a grounded O2, but this is evidenced by blown fuses (several fuses, it seems), and a few with bad CPS connectors.
My car is very original and nobody has messed with much of anything - under 60k and still had the original TB when I got it.

JHowell37

If I start mine when cold, run it for a minute or two, shut it off, and then try to restart it can be a bit difficult at times. Like it has flooded. For me, on one or two occasions I just floored the pedal like I was trying to start a flooded engine and that did the trick. But in your case that doesn't seem to work.

I just looked at the crude trouble shooting chart in the WSM. The symptom "engine hard to start" is likely caused by one of three things.
1. Ground and plug connections.
2. Temp-II sensor
3. Crank position sensor (i.e. reference sensor)

Other then the starting problem, does the car run fine?

Mrmerlin

Larry on the CE pugs, I would suggest that you get a light and remove the lower wood piece in front of the CE panel and carefully check the backside of each of the connectors, ( the side that the wires plug into)what i found is that if the connectors are removed from the board and not put on a certain way then the CE panel pins will sidestep the individual connections and thus miss connecting and slide along the retention pin of the female part of the connector , this will give a intermittant connection, .
So what you will see is the rear side of the connector housing with a connector looking like it sticking out further from the back of the connector body, than the rest of the connectors.
The fix is to take a small piece of wire and insert it into the rear of the connector to push the retaining pin into the connector then pull out the connector and straighten this piece then reinsert it then look at how the connectors can move in the connector body and twist the connector housing the correct way so they all find their respective mates

Larry Velk

This car has a long story. I've owned it for a few years. I do all my own work, but it has needed little. I did the TB, H2O, frt shocks, align (myself), and I have a nice shop and tools to do this. However, the car has always very, very occasionaly stopped within about 30 seconds after it is started - 5 sp, BTW. Also it almost never starts on the 1st crank, but I attributed this to a drain back valve and it hasn't been a problem. I do, however, just crank it a bit, then redo and it goes. One time, and only once in a few years, it lost power at highway speed for a few seconds and then recovered. It has Authority chips and these made little difference. When I got the car it had a 'mouse house' over the air filter so the MAF is suspect as maybe this damaged the unit. When first purchased I also did the wires, plugs, checked the coils, replaced a collapsed vac hose and of course replaced the moused-up air filter. I still need to probe for 12v at (I think) U11 and U12 to see if the 30 terminals are powered.
I'm not wild about pulling the board down as messing with stuff that isn't broken isn't my style - but I see what you mean after seeing how the back of that board looks

I've now spent quality time with the manual - I tried to include a simplified diagram of the 1986 relay circuits. These need to be reviewed and edited if needed. The EZF looks like the 'big boy' that powers up with the ignition on and stays on. This looks like the one that is disabeled by the alarm, so it seems the most critical. This is most definitely not an '87 and up or a pre '85. I put it up since much talk on this topic isn't clear as to the year and some experts weren't sure how the '86 worked.