1985 928S crank but no start
10-12-2016, 11:45 AM
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1985 928S crank but no start
I recently assumed ownership of an 85 928S from my father, who owned it mostly trouble free since 1989. VIN is ***860358. It was seldom used for the last 10 years but always started on demand. About a month ago I drove the car about 30 miles and then put it up on blocks to give it a thorough cleaning and maintenance update. In addition to the oil/filter and air filter swaps, I removed the intake hardware to clean it all up, and spent a fair amount of time under the engine bay cleaning off the worst of 30 years of road grime. I also replaced the front air dam and replaced or repaired some of the associated hardware. After all this (about three weeks) I went to start the car and it cranked but would not fire. I have read through various threads in this forum and tried a few things, but before really digging in I'd like to know if I am missing something simple from the work I have done above, like a vacuum hose or something I missed reassembling the intake hardware.
- I have double checked the vacuum connection to the left bank and the PCV (I think) hose on the right bank.
- I have checked the battery (12.91v with engine at rest), and the connections to the terminals.
- I tested relays 4,16,20,24 and they are working (I swapped them with my 944 horn relay and they all operated the horn) but I have not replaced them yet.
- Central locking system is intermittent.
- Rear trunk will not latch closed, so you have to use the key to lock it. When you remove the key, the alarm sounds so you have to turn it off at one of the doors. This has been the case for at least the last few years. Because of this malfunction I sniffed around the threads about the alarms and would be happy to disable mine as I do not have concerns with security. Problem is I looked for the "Z plug" but could not find it anywhere on my fuse/relay panel. Also I do not know if or where the alarm system hardware is or whether it is factory or not.
My diagnostic ability is limited and I have no test tools other than a voltmeter, but I've done most work on my '87 944S since I bought it new, so I am not afraid to dig in. Thank you in advance for any help offered.
- Dave (pits928s)
- I have double checked the vacuum connection to the left bank and the PCV (I think) hose on the right bank.
- I have checked the battery (12.91v with engine at rest), and the connections to the terminals.
- I tested relays 4,16,20,24 and they are working (I swapped them with my 944 horn relay and they all operated the horn) but I have not replaced them yet.
- Central locking system is intermittent.
- Rear trunk will not latch closed, so you have to use the key to lock it. When you remove the key, the alarm sounds so you have to turn it off at one of the doors. This has been the case for at least the last few years. Because of this malfunction I sniffed around the threads about the alarms and would be happy to disable mine as I do not have concerns with security. Problem is I looked for the "Z plug" but could not find it anywhere on my fuse/relay panel. Also I do not know if or where the alarm system hardware is or whether it is factory or not.
My diagnostic ability is limited and I have no test tools other than a voltmeter, but I've done most work on my '87 944S since I bought it new, so I am not afraid to dig in. Thank you in advance for any help offered.
- Dave (pits928s)
10-12-2016, 12:58 PM
#2
Three Wheelin'
Welcome Dave, glad you are jumping in on it.
Before you go crazy with diagnostics, I would pull the battery and take it down to the local parts store for testing -- unless you just replaced with new.
The S3 requires a tremendous amount of crank amps IMHO. Even though your volts are reasonable, it may still be a battery issue, or even not fully charged.
Before you go crazy with diagnostics, I would pull the battery and take it down to the local parts store for testing -- unless you just replaced with new.
The S3 requires a tremendous amount of crank amps IMHO. Even though your volts are reasonable, it may still be a battery issue, or even not fully charged.
10-12-2016, 03:55 PM
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Welcome to the pit, Pits!
I doubt it is the battery. If it turns over fairly normally, there is enough juice to start...unless cranking slows down severely after cranking for a few seconds. Generally a battery greater than 12.8V will suffice. Could be in need of charging all the same.
Another simple check is the fuel pump Fuse. That one melted on me one time (poor/dirty contacts). Do you hear the pump running while cranking? Try removing and replacing the fuse a couple of times.
Other than that, depending on how much stuff you removed around the intake, you may have disturbed the CPS connector, which is usually crumbling at this age.
Ground wire connections, including the 2 at the top-rear of the engine, should be cleaned.
Are the spark plug wires connected in the proper order?
Simple stuff first! Cheers.
I doubt it is the battery. If it turns over fairly normally, there is enough juice to start...unless cranking slows down severely after cranking for a few seconds. Generally a battery greater than 12.8V will suffice. Could be in need of charging all the same.
Another simple check is the fuel pump Fuse. That one melted on me one time (poor/dirty contacts). Do you hear the pump running while cranking? Try removing and replacing the fuse a couple of times.
Other than that, depending on how much stuff you removed around the intake, you may have disturbed the CPS connector, which is usually crumbling at this age.
Ground wire connections, including the 2 at the top-rear of the engine, should be cleaned.
Are the spark plug wires connected in the proper order?
Simple stuff first! Cheers.
10-12-2016, 06:52 PM
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I agree with Brian^^^
Bad fuel pump, bad fuel relay, easy to check. You can easily bypass the relay with spade connectors if necessary.
Also could be CPS failure. You should replace it anyway, generally easy, it is due to be replaced if it is still original. I agree that you probably disturbed it in cleaning, especially if you had your air filter box off.
I assume you didn't use a high pressure water jet to clean the engine? If so, then it could be a multitude of other things.....
Bad fuel pump, bad fuel relay, easy to check. You can easily bypass the relay with spade connectors if necessary.
Also could be CPS failure. You should replace it anyway, generally easy, it is due to be replaced if it is still original. I agree that you probably disturbed it in cleaning, especially if you had your air filter box off.
I assume you didn't use a high pressure water jet to clean the engine? If so, then it could be a multitude of other things.....
10-12-2016, 07:01 PM
#5
Rennlist Member
Agree with above.
But first, ensure distrib caps are clean from corrosion inside. Then top off battery. Then attempt start with foot to floor. four or five times. Long pulls. See if it doesnt clear flooded condition and start for you. Be prepared for much gas laden white exhaust discharge.
If not, cps replacement.
But first, ensure distrib caps are clean from corrosion inside. Then top off battery. Then attempt start with foot to floor. four or five times. Long pulls. See if it doesnt clear flooded condition and start for you. Be prepared for much gas laden white exhaust discharge.
If not, cps replacement.
10-12-2016, 07:13 PM
#6
Three Wheelin'
Sooooooooo, I don't want Dave to get lost in the weeds here.
If we can't vouch for a fully charged battery -- we probably should before we take it further right? Since the original post was "what easy thing can we check first?"
We would all agree that sharks need > 12.5 strong volts and multiple good grounds to start.
If we can say that battery is fully charged and functional, then I agree we proceed as you guys said.
The things I would look at next...every connection that was recently touched in recent servicing -- make sure nothing was left unconnected when buttoning up.
Then FP fuse, Ignition/Starter/FP relays.
Then battery ground strap and other grounds.
Then 14 pin connector for corrosion.
Then I would remove vac connection from dampers and FPR....if fuel smell replace.
Check TPS short harness for failure, same for CPS as you guys mentioned.
Then check fuel, spark and off we go.
Hell, I would then try a WOT start....S3's like the cobwebs blown out every now and again.
If we can't vouch for a fully charged battery -- we probably should before we take it further right? Since the original post was "what easy thing can we check first?"
We would all agree that sharks need > 12.5 strong volts and multiple good grounds to start.
If we can say that battery is fully charged and functional, then I agree we proceed as you guys said.
The things I would look at next...every connection that was recently touched in recent servicing -- make sure nothing was left unconnected when buttoning up.
Then FP fuse, Ignition/Starter/FP relays.
Then battery ground strap and other grounds.
Then 14 pin connector for corrosion.
Then I would remove vac connection from dampers and FPR....if fuel smell replace.
Check TPS short harness for failure, same for CPS as you guys mentioned.
Then check fuel, spark and off we go.
Hell, I would then try a WOT start....S3's like the cobwebs blown out every now and again.
Last edited by Crumpler; 10-12-2016 at 09:09 PM.
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10-13-2016, 04:51 PM
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Thank you all!
You'll have to nurse me along a little - location of CPS connector and Temp II? Is there another name for CPS connector? Went to 928 Int'l to order and could not find it.
Battery was manufactured in 2014 and kept on a maintainer when not in use. It was able to crank the engine easily multiple times when trying to get it going so I believe the battery is in good shape. I will top off and try Landseer start process after replacing fuel pump fuse, and will listen for the fuel pump during start process.
Dave
You'll have to nurse me along a little - location of CPS connector and Temp II? Is there another name for CPS connector? Went to 928 Int'l to order and could not find it.
Battery was manufactured in 2014 and kept on a maintainer when not in use. It was able to crank the engine easily multiple times when trying to get it going so I believe the battery is in good shape. I will top off and try Landseer start process after replacing fuel pump fuse, and will listen for the fuel pump during start process.
Dave
10-13-2016, 05:20 PM
#10
Rennlist Member
CPS = Crank Position Sensor, does the tach jump at all when cranking, this can be a sign that it's sending a signal but not always a good signal
Temp II is located on the water bridge, drivers left hand side.
Do you have Spark?
if so than the CPS is working, use a Timing Light and see if it blinks when cranking, pic any of the 8 plug wires, I would test one from each distributer.
If spark is good than its a fueling issue, change out the Relays for the fuel pump, LH and EZF w/ new (cheep enough) and you will want to have spares anyway.
Oh and did you check and clean all the Fuses?
Pull each and wipe contacts w/ WD-40 and push/pull in/out a few times to clean contacts.
if you done all the above and still no spark, change the CPS (it's on the top of the Bell closest to the engine).
Dave K
Temp II is located on the water bridge, drivers left hand side.
Do you have Spark?
if so than the CPS is working, use a Timing Light and see if it blinks when cranking, pic any of the 8 plug wires, I would test one from each distributer.
If spark is good than its a fueling issue, change out the Relays for the fuel pump, LH and EZF w/ new (cheep enough) and you will want to have spares anyway.
Oh and did you check and clean all the Fuses?
Pull each and wipe contacts w/ WD-40 and push/pull in/out a few times to clean contacts.
if you done all the above and still no spark, change the CPS (it's on the top of the Bell closest to the engine).
Dave K
Last edited by davek9; 10-13-2016 at 05:36 PM.
10-14-2016, 05:06 PM
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I cleaned up the distributor cap and rotor as per Landseer and tried to start with foot to floor 3 or 4 times, for a minute or so of cranking time - nothing. At least that answers the battery question - it cranked strong the whole time. Timing light shows no spark. Will swap out all fuses and relays then try again. Will advise. I located the CPS connector - I did not disconnect it during cleaning. It does not appear worn but will replace as next step. I'm curious - The CPS connector appears to be an access port of some kind - the CPS does not appear to be connected by wire to anything. Can someone enlighten me how the CPS ties to ignition? Thanks
10-14-2016, 07:04 PM
#13
Rennlist Member
That probably is not the CPS connector. That IS a test port. The connector for the CPS is under the fuel dampeners/regulators.
Last edited by soontobered84; 10-18-2016 at 12:28 PM. Reason: correction by deletion
10-16-2016, 12:05 AM
#14
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Like I said it's the one closest to the engine block (edit: it is actually in the BLOCK), you found the no longer used test sensor.
the one you want has a conection to the engine wiring harness as said below the Fuel lines.
the one you want has a conection to the engine wiring harness as said below the Fuel lines.
Last edited by davek9; 10-17-2016 at 02:11 PM.
10-17-2016, 08:31 PM
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Thank you, I have located the CPS connector, so all set there. I found a poor ground connection between the back of the engine block and the body, so cleaned that up and tried again, - no start but got a spark response from the timing light. Cranked with foot to floor again but no start - smelled fuel after a few pulls so I stopped. I'll check the other grounds and then replace all fuses and relays tomorrow.
I found a few of the spark wires to be partially melted or and/or very brittle, so I'm going to replace them and the plugs as well while I am at it. I did not disturb the CPS but will replace anyway if that is believed to be a potential problem in the future. I have the part number for the CPS as 944.606.115.00. 928 int'l calls it an impulse sensor (flywheel). Any suggestions regarding these purchases is appreciated. If you know of any other parts that should be replaced because it is considered a matter of time before it strands me please let me know.
I found a few of the spark wires to be partially melted or and/or very brittle, so I'm going to replace them and the plugs as well while I am at it. I did not disturb the CPS but will replace anyway if that is believed to be a potential problem in the future. I have the part number for the CPS as 944.606.115.00. 928 int'l calls it an impulse sensor (flywheel). Any suggestions regarding these purchases is appreciated. If you know of any other parts that should be replaced because it is considered a matter of time before it strands me please let me know.