No Stop Problem

[ljmazzoli]

Purchased a 1983 project 944. Car ran but needed a bit of TLC. Finally got car back together and had no start problem (prior post). Replaced DME, and fuel pump fuse and all starts and runs well. Now the problem is no stop situation. I can turn key off and remove from ignition and car continues to run until I remove DME relay.

Replaced ignition switch, but same problem. Tested wires at ignition switch and they are on and off as they should with key in diffent positions, so that seems to be working well. Posted on Rennlist and received a few replies, but not successful so far troubleshooting this problem.

I guess this is better than no start situation, but would like to get this resolved. any thoughts?

[944 Ecology]

Sounds like something is powering the ignition coil and the DME relay, which in turn is powering the ECU and the fuel pump. I'm going to guess a problem with the fuse block. Use the wiring diagram to check the 15 circuit (switched 12 vdc from the ignition switch).

[Monkey Wrench]

How many fuses does the car actually "need" to still have installed, to keep running? If you know that then maybe it would lead you in the right direction to discover how the power is getting there when it should not.

thinking in the way of shutting off all other circuits by removing the fuse, in order to narrow it down so you know which circuit is feeding it.

Kind of nice to know aside from this issue, how many fuses are important for the car to run.. then you know or maybe have a better idea, which circuits are Not related to to feeding the DME/ Pump or necessary for the car to be in a running situation.

the other obvious question is did you do anything else recently with respect to the electrical system before this problem occurred? look there first. recall any accidental shorts? could the relay have welded it's contacts,maybe due to an overload caused by who knows what, accidental short circuit maybe? was the relay installed at the same time as a bad fuel pump?

maybe pull the DME relay and referring to the schematic, or with help from those more educated , figure out which contacts "should be" turned on by the coil, then check the relay itself, whit a meter with the relay removed,

See if you have continuity between those contacts which are assumed should be open with no power to the relay coil. I know its a bit more complex than just a single set of relay contacts.

. if those contacts welded themselves in closed circuit mode then the contactor may not open as they should and thus still supply power when they should be open.

a situation wehre the relay was trying to supply an abnormal amount of power , say a short circuit like a bad pump , then it might try to conduct way more amps and weld the contacts in a closed position in the relay. coil circuit might go off like normal when key is off , but contacts are welded so they stay closed, despite the state of the coil having power or not.


to be fair here, I'm not as experienced with this particular circuit as some of the the others here so please take that into account too. just some ideas..

[ljmazzoli]

I have looked throughout the engine compartment and around the relay/fuse block and see no sign of wires touching others that should not. I removed the relay holders from the fuse block and removed all the colored connectors going into the block as well and see no sign of anything causing a short. All wires and connectors and seem in good shape.

I have checked the wires at the DME relay and the fuel pump and ignition wires do not have power until the ignition is turned on, which i think is correct. When I turn the key off and the car keeps running i check power a the fuel pump and ignition wires and they still have power. I disconnect the DME relay to kill the car and plug it back in and no power to the fuel pump or ignition wires. When i disconnect the DME relay it almost resets something and goes back to normal. With this situation, I feel that some other relay isn't resetting after the ignition is turned off. I have tried three other DME relays and they all act the same.

I feel like just installing a cutoff switch to turn the car off. I will agree this is much better than no start situation, but driving me insane searching for the fix. Curious if it could be a DME ECU problem?

[originalowner]

Per my advice to you over on Rennlist, check for continuity between DME relay socket pins 87 and 87b. It would completely explain what you are observing.

[ljmazzoli]

Originally Posted by originalowner

Per my advice to you over on Rennlist, check for continuity between DME relay socket pins 87 and 87b. It would completely explain what you are observing.

I have no continuity between 87 and 87b on the relay

[Monkey Wrench]

so when you check the relay with it unplugged , its showing the contacts as open as they should. when you turn the key off the car continues to run. If you pull the relay then the car dies. check with the others but i think the DME also supplies power to the fuel injection so that might make it die anyway.

what if you remove the cover of the DME relay , can you see if the contacts to the fuel pump are opening when you shut the key off?



should there be two sets of contacts in there that both should shut off with the key?

maybe when you pull the relay the contacts separate.. perhaps you could get out of the car with the ignition off and then while the car is running give each relay, but especially the DME a tap with the handle of a screwdriver to see if any dislodge and if that might make it turn off. In other words Jarring the relay , or pulling it out, might shock it enough to dislodge the contatcts.

frustrating as it is I wouldn't resort to turning it off some other way. there is going to be one cause and the solution will be easy, its finding the actual cause that needs focus.

I thought maybe if you had issues with the fuel pump being bad you might have have had all 3 relays in there and maybe maybe with the defective pump drawing a lot of current could damage them all.. Then again, I could just be jumping to conclusions with that.

Id run a couple of tiny 12 V low watt indicator bulbs with small wires going to the terminal(s) that the relay turns on , plus a ground wire so you can actively see the power to the pump and maybe power to other things the DME switches. That shouldn't change things at all from an electrical perspective but may help visualize things better during troubleshooting.

i think the added load is very negligible but even if that was a worry the indicator bulb could have a switch to turn it off except when testing.

this won't tell you anything the meter can't . but for me anyway, that sort of thing helps me simplify what I'm looking at and maybe lets you do a check without going looking for the meter and trying to access valid test points. you can monitor things more in real time than just by performing a test with jumpers, clips etc.

at the side of the road with a car down maybe that helps troubleshoot when you may not feel comfy getting the meter out and focusing on electrical diagrams and proper troubleshooting sequences. Just knowing whether or not you have power to the pump at any given moment can be helpful. crawling under the car with a meter to probe the fuel pumo is awkward, you cna pick up the same connections under the hood. if you run int a condition where the light is on but pump isn't running then you can troubleshoot why that is after, but then you know its the pump or the wire between.

right now what you are reporting is that the DME is unlatching and power is being supplied to the pump some other way and maybe that's possible but I don't have an answer to that puzzle.

what I think a test light light might tell you is ...

Is it unlatching when in circuit, and not just unlatching because it is jarred when you pull the relay?

if the cause is the relay welding I'd expect that to be sporadic and not a consistent pattern.

usually cars have an accessory position , that might ( for example) run the radio with he ignition coil turned off. Now If one were to somehow accidentally connect to both the start and run position to feed power to that radio, then maybe the run position could be back-fed. electrically speaking that might look like a jumper wire between the start and run position.

Physically it could be anywhere supplied by both the the accessory position and the run position being accidentally connected. Bad key switch maybe but I wouldn;t go trying to tke the ignition apart without better evidence of that.

maybe you could probe more easily accessible parts of both accessory and run circuits to see if they might be interconnected. wiring near the key might be award to access, so what does ignition power, what does ignition on on also power? is there resistance between the two or zero ohms? I guess a question that could come before this is does the key have an accessory position? maybe inserting the key is the accessory position . If it is sitting there running, but not in the run position, will pulling the key out make any difference?

if we were to make a list of things that work in the accessory position and things that work in the run position , would you notice any changes. IE Any other things that shouldn't work when the key is in accessory but do ?


in some cars the radio may only work when the car is running so what people do is turn the key to run while they are sitting int he car waiting for someone. they dont start the car. Ive found that in other cars, the ignition coil can get warm under that condition. I think in the accessory position, the coil should not be on, if the key has an accessory position.

you might put a jumper on the coil wire the other to ground then turn the key to various positions. when you turn the key to off , is the ignition coil still on? if it is , then why? Next, is the ignition coil fed through the relay or from the key wiring itself? pull the relay and again check the power state of the ignition coil in the different key positions.

excluding confusion around the DME relay . is the ignition coil receiving power with the key in the off position? if so, why?


aftermarket radios are often added by people who dont understand a lot about wiring so I could see them picking up the power from the wrong location or even maybe form more than one location thus interconnecting the two power sources. I've seen some really amateurish radio installation wiring.

a radio may have a constant power wire to retain memory, a power wire so the radio comes on in the run or the accessory position, or both.. Also sometimes there is a wire to feed a power antenna so that when the radio is turned on the antenna is lifted. that wire could be mistaken for some other wire and powered rather than being run to it's intended load which is an antenna motor.

its common for people to pull a radio from one car , hand it to some other person and in the process, lose track of the proper connection info.

d rather have my radio work all the time or in an accessory position because then Im able like to listen tot he radio without the key on and powering the coil.

why a coil gets hot under that condition I'm not clear on , maybe there is some reason like something wrong but I remember getting a coil quite hot by simply leaving a car with the ignition on and not running.


investigating this a bit better might prove wheather or not that coil power goes through your DME relay or maybe it's just wiring from the key to the coil. If it was the key switch itself that was the issue, then you might also notice that the coil also has power with ignition in off position.

if you find your coil is on with the key turned off, even with the relay unplugged, then I'd look fro some other issue than a bad DME relay.


studying the diagrams or asking someone more familiar might tell you whether or not the DMV relay has anything at all to do with providing power to the ignition coil ,. If it does not , and it is powered on when it should not be, then you found another condition which seems abnormal. the next question then might be why is the coil hot when the key is off? If it's doing that with the DMV unplugged then the ignition coil must be getting power from some source unrelated to the DMV relay. that might lead me in the direction of problems within the keyswitch.

[originalowner]

Originally Posted by ljmazzoli

I have no continuity between 87 and 87b on the relay

Did you check for continuity on the relay, or the relay socket?