Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

1981 S2 DITC Car - Sudden no start issue

 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
stevekat  



Joined: 19 Jan 2008
Posts: 718
Location: Los Angeles, CA

PostPosted: Thu Jun 13, 2013 2:34 am    Post subject: 1981 S2 DITC Car - Sudden no start issue Reply with quote

Last night I was driving my 1981 S2 DITC car (with factory CGT intercooler) and when we came to a light she stumbled and shut off. I could not get her restarted. Occasionally I shall get a misfire and just have to reach down and wiggle the DITC box connector. This seemed different.

This car has been absolutely reliable. She starts instantly in all seasons, in all circumstances.

I replaced the DITC box with a known working unit, and also the ignition unit, as I have spares of almost everything. This made no difference. I happened to have the battery out the other day an noticed the three tap wires were a bit loose on the terminal, so I tightened that down, and tried her and she started right up. I then swapped the original ignition unit back in, but left the replacement DITC in for convenience, and again she started right up, instantly.

I packed up my stuff, and when I was ready to drive her back home, she would not start again, and that is where I left it, bringing her back to my place.

I separated the two white connector behind the coil, double checked the big DITC connector, etc.

I have some spare sensors and they all read about the same...8.5 ohms between one set of pins, 8.7 or so between the another set, and 0.7 on the last set. The set in the car reads about this too. Maybe 9 ohms on the higher pins.

One question I have is is there experience testing the sensor in-situ, and getting pretty good readings, but it turns out the sensor is bad, and all was well when it was replaced?

I see a couple of threads that describe almost identical circumstances, but the OP never circled back to close the circle. I have a PM out to one to see how they ended up.

So any insight, experience, suggestions, are welcome. One note, is that I know these cars pretty well.

Thanks!
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.
Back to top
View user's profile Send private message
morghen  



Joined: 21 Jan 2005
Posts: 8201
Location: Romania

PostPosted: Thu Jun 13, 2013 3:08 am    Post subject: Reply with quote

Does the fuel pump work and actually deliver fuel?
Try to replace the flywheel sensor with a known working one.

Jeez these sensors are becoming a scarecrow...time someone got off their ass and find a replacement for that thing.
How hard can it be? i'm sure its just a coil..
_________________
SUPERCHARGED Ruby-sh 924
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
ideola  



Joined: 01 Oct 2004
Posts: 15506
Location: Woodstock IL

PostPosted: Thu Jun 13, 2013 3:50 am    Post subject: Reply with quote

I wouldn't be so fast to assume it's the sensor. You do need to confirm that the fuel pump is functioning. There are multiple reasons it may not be, and the sensor is only one of them.

First suspect: Are you sure the boost cutoff switch hasn't failed or become disconnected? I have had this happen to me: on one car the sensor itself actually failed; on the other, the wiring failed. You need to eliminate that from the equation first. Disconnect the line and ground it out (make a jumper lead with male spade terminal on one end and ring terminal on the other; pull the line from the boost cutoff switch, connect the male terminal of your jumper there, and connect the ring terminal to one of the bolts on the back side of the alt or anywhere else on the head or block that is convenient to reach).

On one of my cars, this line was in pretty bad shape and I had to cut it off way back under the intake mani and splice in a fresh section of wire.

The other thing is to make absolutely certain all of the connections at the coil are working correctly. On the same car, one of the wires there had the insulation cracked and falling away, and the wires had become badly corroded. No signal at the tach, no start.

If you do want to swap out the sensor it's really not as bad as you might think. Remove the coil to provide better access in that area. Loosen the integral wire clamps along the firewall and move them up and out of the way as best you can. I use a 10mm socket (1/4" drive) with several long extensions. Get the bolt loose but do not remove it. Then get a mechanics extending magnet and pull the bolt and the little shim underneath the sensor out. From the inside of the car, disconnect the electrical plug at the DITC box, and remove the grommet from the firewall. Now go back under the hood and pull out the sensor.

Replacement is basically the reverse. I use one of those little expanding claw tools to get the bolt back into position. It's a bit tedious, but it can be done.
_________________
75 Fiat X1/9 | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 Poli-Form
Back to top
View user's profile Send private message
stevekat  



Joined: 19 Jan 2008
Posts: 718
Location: Los Angeles, CA

PostPosted: Thu Jun 13, 2013 4:27 am    Post subject: Reply with quote

I am going to put a gauge on the CIS - I have one from unwired tools in addition to the full tester, but I believe I have no spark. In any case, I have a switch box I made a long time ago for diagnostics to jumper the fuel pump relay connectors on the fuse box for when I ever need to run the fuel pump independently.

What I'd really like to know is if the sensor can report the correct resistances but not be operational.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.
Back to top
View user's profile Send private message
!tom  



Joined: 28 Aug 2006
Posts: 1905
Location: Victoria, BC Canada

PostPosted: Thu Jun 13, 2013 2:47 pm    Post subject: Reply with quote

Don't forget simpler causes, such as the ignition key switch.
_________________
78 924 NA
5-lug
Back to top
View user's profile Send private message Visit poster's website
stevekat  



Joined: 19 Jan 2008
Posts: 718
Location: Los Angeles, CA

PostPosted: Thu Jun 13, 2013 3:18 pm    Post subject: Reply with quote

I got her started and running as before.

Matilda, who had an earlier thread, responded to a PM and indicated he had replaced his DITC sensor and it made no difference. So my take away may be that if a sensor tests good on the ohmmeter, it may be good.

Matilda said his tech and he discovered that there was not always 12v at the coil. And that some connection in the vicinity of the fuse box had become flaky. I checked for voltage at the coil and either had none or 1 - 2v. I reached under the fuse box and disturbed the wire bundle and it shot up to about 12v. At that point I turned the ignition and she fired right up and ran as normal.

I then disconnected the battery, pulled the fuse box down and inspected and disconnected a few plugs, etc. On putting it all back together she continued to run. It may come back, as I don't know I figured out the specific culprit, other than pulling some connectors and re-seating them.

But in general, it was power to the coil and this is very easy to test. The wire to the coil is black and blue (and I think there is a black too.)

I think an easy fix to this in an emergency is to jump a wire from the positive of the battery to the positive of the coil. If the DITC and other ignition components are functioning properly, as mine were, and all that is missing is power to the coil, this should make the car run as it should.

So Matilda and I had this problem, and I've seen similar descriptions of it, so this may be some kind of common weak spot. I think there are two paths for power to the coil, during start and during run. One or both may originate at the starter, but I did not crawl under to inspect there. I am sure another member is more familiar with this wiring.

One note, do not disturb everything when hunting these things down. If one replaces a DITC box or ignition module and it does nothing, switch it back. It is important to keep this a one variable equation.

Also, I'd like to encourage all who have issues they eventually resolve to report back with their results. So many threads just trail off, describing very compelling problems, and one wishes the solutions that were found get added to the dialog.

Thanks to Matilda for responding to my PM's about his experience.

And thanks for the feedback.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.
Back to top
View user's profile Send private message
ideola  



Joined: 01 Oct 2004
Posts: 15506
Location: Woodstock IL

PostPosted: Thu Jun 13, 2013 10:25 pm    Post subject: Reply with quote

Steve, this jogs my memory regarding an issue I found on GEBLASN, the S2 931 that my son was driving for a while, which I sold last year.

One of the spade terminals on the back of the relay holder for the fuel pump relay had come loose, such that when you inserted the relay, it would make a connection at the tip of the relay terminal, but it would literally push the female spade receptacle out of the relay holder. So the relay was not seated properly in that one specific connection.

The entire time I owned the car, we had trouble with sporadic DITC-like symptoms. The car would run great, and then suddenly it would misbehave. I did all of the usual DITC troubleshooting, but the problem would always come back.

As it turns out, the little tab on the end of the spade terminal had gotten deformed to the point that it was no longer securing the spade terminal in the relay holder. So when you tried to plug something in to it, it would make contact but slide backward. Then during driving, it would sporadically interrupt that particular circuit at the relay, causing the sporadic fuel cut issues that I now believe were one of the root causes of the problems we experienced all along. I believe the mangling of that spade terminal was from repeated removal and installation of various relays and jumpers while conducting all of the tests and troubleshooting that were required to resurrect this car.

What I would suggest based on what you wrote is to pull the fuse block back down and double check that specific relay holder and make sure all of the female spade terminals are firmly seated and can't be pushed out from the front or pulled out from behind.

On GEBLASN, I don't recall if I was able to bend the little tab back into proper position, or if I cut off the old one and put a new one on. I keep a stash of that style of spade terminal in my electrical kit now.
_________________
75 Fiat X1/9 | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 Poli-Form
Back to top
View user's profile Send private message
stevekat  



Joined: 19 Jan 2008
Posts: 718
Location: Los Angeles, CA

PostPosted: Sat Jun 15, 2013 1:31 pm    Post subject: Reply with quote

Dan, thanks for the tip. In this case I do not think it was this issue. I had jumpered the fuel pump terminal with a special switch box I had built for this purpose in the past as a back up, so I had the pump running manually for some of the process I used to figure it out. The issue in this case was power to the coil, rather than the fuel circuit. The fuel pump does tap a signal from the coil (the pulse that the fuel pump needs to turn power on to the pump) but it does not effect power to the coil as far as I know. The wire is a black and blue wire to the coil (thought another wire comes into the same terminal.) I do not recall completely, but power for the coil may come from the starter tap, for either the starting and/or operating voltage to the coil. Just have not had time to check the diagram. With everything else working (DITC, ignition module, sensor) running a wire from the battery to the coil can solve the problem in a pinch if power to the coil is absent and is the sole issue. I dropped the fuse panel and pulled and reinserted the plug (blue) that I believed represented power to the coil during the process.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 10 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group