cainhead Posted February 7, 2020 Share Posted February 7, 2020 Hello, Got a few issues with the car starting and trying to work out if maybe they are linked. The car is a UK single with an AEM V2 ECU. Sometimes when I try to start the car it turns over fine but doesnt start. I have to turn the key back a click and then back again. Once I here the fuel pump prime i know it will it start. But on occasion I have to turn the key back and fourth a few times. I spoke with AEM and they were very helpful, the guy said it sounded like something aftermarket was interfering with the shutdown sequence. Basically making the ECU think its not shutdown and therefore not resetting itself to the start sequence. He backed this up with by giving me a test to do involving turning the key back taking of the negative terminal of the battery, replacing it then turning the key back to on. Fuel pump primes every time. My guess is the immobiliser is the offending item. Just wondered if anyone else has had this issue. Im also getting a flat battery quite regularly. Battery is a new redtop and I have also replaced the alternator for a brand new one. Could this be linked to the immobiliser? I was thinking I would try and disconnect the immobiliser and see if that helps the starting and battery drain. Also checking that the alternator is sending charge back to the battery. Could anyone recommend the best way to test this? Lastly when the car fires it splutters a bit, i give it a little gas and it coughs itself into action. But 1 in every 4 starts it wont hold idle. It just stalls. It still drives but I have keep a bit of gas on when coming to a stop. Strangely it sorts itself out after a while driving. I put a brand new TPS in but still doing it, but as I say it's only 1 in every 4 starts. Apologies for the long winded emails but thought I would try and work on all my issues in one go as some may be connected. All replies and help much appreciated. Cheers - Quote Link to comment Share on other sites More sharing options...
Mo Reviews Posted February 7, 2020 Share Posted February 7, 2020 (edited) Does this usually happen when the car has been left unlocked for a while prior to an attempt to start it is made? If so, have you tried putting the key in, turning it twice to accessory then hitting the unlock button on your key fob before attempting to start it? As for the other idle issue, does this usually happen on a cold start? Sounds like a cold start map issue that has been exacerbated by the cold weather... Edited February 7, 2020 by Mo Reviews (see edit history) Quote Link to comment Share on other sites More sharing options...
cainhead Posted February 7, 2020 Author Share Posted February 7, 2020 I don’t leave the car unlocked enough or for long periods of time to really answer that. My worry is the AEM not shutting down properly due to the immobiliser and drains the battery somehow. As for the idle it’s not just cold starts. I’ve reloaded the original map a few times as I had no issues like this for the first couple of years. This only really started last summer. Since then I have been replacing some of the main ignition parts for brand new to try and sort. Cheers Does this usually happen when the car has been left unlocked for a while prior to an attempt to start it is made? If so, have you tried putting the key in, turning it twice to accessory then hitting the unlock button on your key fob before attempting to start it? As for the other idle issue, does this usually happen on a cold start? Sounds like a cold start map issue that has been exacerbated by the cold weather... Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 9, 2020 Share Posted February 9, 2020 You need a means of monitoring fuel pressure on key on after a long period of being switched off. The system should hold some rail pressure with key off for hours, and on key on immediately rise to working pressure. An electronic or mechanical gauge will work, does the rail have an external fuel pressure connection valve? If not you need to get some appropriate adaptors to measure pressure after the fuel filter and before the return valve. Monitoring the mixture immediately after a cold start is tricky as a wide band sensor needs to heat up before giving correct readings. You should also measure the voltage from the ECU water temp sensor at start up, in real time or by looking at the logs to see if it's a temp sensor issue. A bit of well thought out measuring should show the issue without throwing parts at it. A crude test is to hard wire the pump to run just before trying to start it and see if it helps, but be careful you don't back feed anything you shouldn't! Quote Link to comment Share on other sites More sharing options...
cainhead Posted February 9, 2020 Author Share Posted February 9, 2020 Thanks for the info Chris, I’ll take a look at the rail today and down load the log off the AEM ecu. It’s a whifbitz top feed rail and kit with a fuel lab FPR if that makes any difference. What pressure value should I be getting? I checked the resistance on the coolant temperature sensor and it seemed about right according to Andy’s chart, and it was getting voltage (5v) at key on. In terms of measureing in real time I guess cutting a small section of the wire sheath away on the plug wires to allow contact for the volt meter would do it. What should the voltage change too? You need a means of monitoring fuel pressure on key on after a long period of being switched off. The system should hold some rail pressure with key off for hours, and on key on immediately rise to working pressure. An electronic or mechanical gauge will work, does the rail have an external fuel pressure connection valve? If not you need to get some appropriate adaptors to measure pressure after the fuel filter and before the return valve. Monitoring the mixture immediately after a cold start is tricky as a wide band sensor needs to heat up before giving correct readings. You should also measure the voltage from the ECU water temp sensor at start up, in real time or by looking at the logs to see if it's a temp sensor issue. A bit of well thought out measuring should show the issue without throwing parts at it. A crude test is to hard wire the pump to run just before trying to start it and see if it helps, but be careful you don't back feed anything you shouldn't! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 9, 2020 Share Posted February 9, 2020 The AEM logs should, or at least i would hope, show the voltage from the coolant sensor during the warm up phase. as to static fuel pressure, engine not running, it could be pretty well anything within quite a range, depends how it was set and then mapped. but about 35 to 50 PSI I would imagine. The mapper should have that info. Quote Link to comment Share on other sites More sharing options...
cainhead Posted February 9, 2020 Author Share Posted February 9, 2020 Okay thanks Chris. It was mapped a few years ago but the issue is only recent. I’ll get a good look at the map and logs a little later. I have to go outside to get to the garage so I’ll get my dry suit on! The AEM logs should, or at least i would hope, show the voltage from the coolant sensor during the warm up phase. as to static fuel pressure, engine not running, it could be pretty well anything within quite a range, depends how it was set and then mapped. but about 35 to 50 PSI I would imagine. The mapper should have that info. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.