Jowniofownio212 Posted July 4, 2019 Share Posted July 4, 2019 Hello i have a problem with my 1983 911sc. When I turn the key to start, the starter motor spins and spins but doesn’t start. 9 times out of 10 I can continue to do this and it still doesn’t start. But if I turn the ignition of then try again, 9 times out of 10 it always starts second time. My way to get it started is try first time for a second or 2 and then stop and start again and it usually does. Any ideas what this could be? Or what to check? thanks Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted July 4, 2019 Author Share Posted July 4, 2019 Just to clarify, the starter motor is turning the engine over Link to comment Share on other sites More sharing options...
mean in green Posted July 4, 2019 Share Posted July 4, 2019 Have you got an ancient immobiliser in the mix? Link to comment Share on other sites More sharing options...
proporsche Posted July 4, 2019 Share Posted July 4, 2019 how about cold start valve -the 7th injector.. Ivan Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted July 4, 2019 Author Share Posted July 4, 2019 2 hours ago, mean in green said: Have you got an ancient immobiliser in the mix? Not that I know of 1 hour ago, proporsche said: how about cold start valve -the 7th injector.. Ivan Any way to test this. Looking at symptoms of the cold start valve, I would have a rough idle at start up cold. I get a reasonably smooth idle after second attempt to start. It also doesn’t start as easy as I would expect. Maybe 4 cranks of the engine or so thanks Link to comment Share on other sites More sharing options...
proporsche Posted July 4, 2019 Share Posted July 4, 2019 no ,you would not have a rough idle after start..you will have a hard starting procedure.To test the injector you have to check the power to it while you crank ,cold.It also comes from your left chain housing cover switch -the wiring. Here is an index of tests... Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted July 5, 2019 Author Share Posted July 5, 2019 Ok, looking at that index, it could be: Auxiliary air valve does not open (although idle seems reasonable) cold start system defective Thermo-time switch defective cold control pressure outside torerance And possibly engine fuel pump not operating Link to comment Share on other sites More sharing options...
Leicestershire Posted July 5, 2019 Share Posted July 5, 2019 Worth checking the fuel pump fuse. The modern plastic fuses can get hot and deform. This gives a poor contact in the holder. Link to comment Share on other sites More sharing options...
Busybee Posted July 5, 2019 Share Posted July 5, 2019 1 minute ago, Leicestershire said: Worth checking the fuel pump fuse. The modern plastic fuses can get hot and deform. This gives a poor contact in the holder. If you still have the bullet fuses, I’d second that. On my sc, before I installed one of Jonny’s boards, my fuel pump fuse used to get hot and had an intermittent fault where it would just lose contact and cut out. Wasn’t restricted to starting though in my case. Check the fuse for signs of heat. New board with blade fuses and no problem since. Link to comment Share on other sites More sharing options...
proporsche Posted July 5, 2019 Share Posted July 5, 2019 i don`t think is the fuse if the car runs after the 2nd restart.Check your fuel pump relay and yes inspect the fuse too....the rest is going with the trouble shooting index...if looks like fuel delivery for sure.. Ivan Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 16, 2019 Author Share Posted August 16, 2019 Right still having this issue and have done some fault finding and am now even more confused. Following the bellow diagram, according to fault find instructions, when I turn the key to start the starter motor, I should have 12v on pin 30 to the fuel pump, I don’t have this. This 12v should come from pin 87 and when I turn the key to start, I have about 10v on 87? Not sure if this is too low or there is something dragging it down. I have bench tested the relay and swapped the relay and get the same fault, once the car does start, there is 12v on pin 30 as I’m guessing the relay is de energised and it is supplied from 87a which is ignition. Im confused about what could be the issue. I am thinking maybe a dodgy contact on the ignition switch? Is there any wiring diagram so I can see where pin 87 is fed from to trace back? thanks Link to comment Share on other sites More sharing options...
jevvy Posted August 16, 2019 Share Posted August 16, 2019 There are some wiring diagrams on the pages following the one that the DME relay schematic you posted above - do you have that manual? Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 16, 2019 Author Share Posted August 16, 2019 No unfortunately not got the manual Link to comment Share on other sites More sharing options...
jevvy Posted August 16, 2019 Share Posted August 16, 2019 This link looks like you can download the manual in 7 parts: http://early911nzdownloads.yolasite.com/workshop-manuals.php My copy is all as one pdf and 70mb so if you would prefer that version let me know and I'll get it to you somehow. Link to comment Share on other sites More sharing options...
proporsche Posted August 18, 2019 Share Posted August 18, 2019 i would say you have a trouble with the 7th injector Cold Start valve Ivan Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 18, 2019 Author Share Posted August 18, 2019 5 hours ago, proporsche said: i would say you have a trouble with the 7th injector Cold Start valve Ivan What makes you think that? Does that effect the supply to the fuel pump as I don’t get 12v on pin 30 to the pump when cranking Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 18, 2019 Author Share Posted August 18, 2019 The quality of the drawings in the manual arnt the best on that pdf. I will try and dig out my Haynes! Reading the manual, it says that the warm up regulator won’t give 12v supply to the pump until engine is fully running so I’m confused as to how it will ever start?? Link to comment Share on other sites More sharing options...
proporsche Posted August 18, 2019 Share Posted August 18, 2019 what makes me think that??you have a problem on the 1st start that is the thinking i have...have you checked it yet? Ivan Link to comment Share on other sites More sharing options...
Northy Posted August 18, 2019 Share Posted August 18, 2019 That low voltage on the red relay is weird. Definitely not an old immobiliser lurking in there somewhere? Have you tried removing the red relay and manually bridging the pins, then cranking it over on the key, if it still does it you can eliminate the red relay and look elsewhere. Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 20, 2019 Author Share Posted August 20, 2019 I have manually put 12v to the fuel pump and it starts fine. But with the relay or any other relay, it usually takes 2 tries before starting. On 8/18/2019 at 3:11 PM, proporsche said: what makes me think that??you have a problem on the 1st start that is the thinking i have...have you checked it yet? Ivan Will look into this next, is there a test procedure to follow that would help? Link to comment Share on other sites More sharing options...
mean in green Posted August 20, 2019 Share Posted August 20, 2019 What about if you jump the relay socket terminals with the relay removed as per Northy's suggestion? (does the fuel pump run then?) 10v at the board seems too low. Link to comment Share on other sites More sharing options...
nealfairfield Posted August 21, 2019 Share Posted August 21, 2019 I had this before and the bolt on the battery terminal clamp was corroded. cheapest replacement part I've ever needed. Shame not the cheapest labour total... Link to comment Share on other sites More sharing options...
Jowniofownio212 Posted August 23, 2019 Author Share Posted August 23, 2019 On 8/18/2019 at 3:11 PM, proporsche said: Been doing some tests. Correct me if this is wrong regarding the fuel pump check valve: Lift the airflow sensor on the engine with the key in the run position and it will turn on the pump and pressurize the system and add fuel to the cylinder to start. If the check valve is the problem, it should start, I lift the air sensor behind the air filter while ignition is on, the fuel pump runs. I then go and start the car and it starts first time! Does this prove the check valve is not holding pressure and I should replace? Thanks Link to comment Share on other sites More sharing options...
proporsche Posted August 23, 2019 Share Posted August 23, 2019 The fuel pump check valve is there for different reason not starting.It is there so when you stop the engine or car it would hold the fuel pressure along with the fuel accumulator.Your problem is somewhere else.Have you checked the cold start vale yet?????????/ Ivan Link to comment Share on other sites More sharing options...
craigt Posted August 23, 2019 Share Posted August 23, 2019 Jowniofownio212 I'm no expert but based on what I do know, and I say this respectfully, you're ignoring the cause in front of you and jumping to conclusions. Throwing parts at a problem is costly and confusing - I've done it 🙈. The check valve is not the culprit here. If you have 10 volts at the relay - that's an issue. Don't ignore it. Ivan has suggested the cold start injector as the cause but you seem to reject that. It seems a likely culprit as first turn of the key provides fuel but not enough to start a cold engine. 2nd turn of the key gets you going as there's more fuel floating about in there. Focus on the facts and be methodical.....good luck and let us know. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now