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Thread: Need Help! after mods car will not start

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    Need Help! after mods car will not start

    First, this has never happened before so I don't even know what happened. Replaced turbos, put the stock airbox and MAF back in. Took AEM out put stock computer and injectors back in. Unplugged the MAP sensor for the AEM. I put it all together, popped the battery back in and it cranks, I get fuel pressure and it sounds good, but I am not getting any fuel in the chamber. The plugs come out dry. I never had that happen. The MFI relay clicks but its not that loud and I thought if I got fuel pressure then it was working but maybe thats my issue? It started fine 6 months ago and I never had an issue like this before. I even put the stock downpipe back in. All of this was done for emissions testing since my inspection is overdue. Its a 1995 VR4 and the ECU was always good and was sitting on a shelf while I used the AEM.

    Thanks
    Sam

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    Oh, and i replaced the PTU also. I have not checked to see if I had spark, but since the plugs are dry thats where I am starting first.

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    Senior (i.e. OLD) Member :) verified Feedback Score 4 (100%) OhioSpyderman's Avatar
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    Wow Sam

    Never using an AEM, I'm not much help, but would you have to splice into stock wiring with the AEM that may somehow mess up the stock ECU (intercept signals to the injectors?).

    There's lots of guys with AEM's on the board so hopefully one of them will have a solution....

    Bob.
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    No, thats the thing. I did this already two years ago. The map sensor is spliced into the TPS for power and taps into the EGT so the AEM can read it. I would just unplug the MAP sesnor so its basically out of the circuit. I put stock injectors back in and repalced the entire ignition (coil packs, plugs, wires, PTU). I put it all back together with the stock downpipe, stock MAF, stock ECU and stock airbox for inspection. The only thing thats odd to me is the not so loud MFI relay click, and the fact that when I put the battery back in, the positive terminal did not arc like it normally does as I attach it after the grounds are already attached. I'll have to check the body grounds--maybe I left them off?
    I never had the car not want to start after mods so I can check the timing to make sure it did not jump while it was off for 6 months and then I can check the cam and crank sensors and the various fuses. The 15amp engine one is good in the car.

    sam

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    Senior (i.e. OLD) Member :) verified Feedback Score 4 (100%) OhioSpyderman's Avatar
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    Sam, do you have a hybrid logger? If not, would you like me to send you mine? (Palm M515 with AutoMirage (ShiverVR4's) software and cable)

    Bob.

    EDIT: It may not help the situation, but at least you'll know that your ECU is working/talking.....

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    Banned Feedback Score 11 (100%) J. Fast's Avatar
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    So it's not starting on the Stock ECU or with the AEM now? You disconnected the negative side of the battery before you chaned any of the wiring? Did you tie the AIT sensor back into the MAF harness?

    As a recap here, going back to stock for emissions you pulled the MAP sensor, AIT sensor, downpipe, injectors, AEM. Installed stock DP and CATS, stock injectors, disconnected and rewired the AIT, disconnected and rewired the MAP sensor, installed the stock EGR, installed stock injectors, installed stock MAF. Plugged the MAF harness back in and it wont start. You observed no fuel in the cylinders?

    Take out a meter and check the ECU ground connectoin at the main harness socket in the ECU. Main ground in your ECU should be pin 26. Tie it to the MFI wire pin which is pin 108. When you turn the ignition to the "on position" you should see o-3V. If you see the voltage go to the MFI and test the signal from the MFI to the PTU. Then PTU to the injector harness socket on the firewall.

    Do the same to the cam and crank sensors which are pin 68 and 69. Ground to pin 26 and crank the vehicle. When your cranking you chould see .2-3v. You are testing to see the rising and falling edges of the contact sensors. No signal... check the sensor in the engine. You can phsically check the edges of the trigger wheel by spinning them. If the sensor has no oscillation its bad. If it does, then it's the ECU. If you don't see the call voltage then it's either a ground or an open wire or the ECU.

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    Thanks Bob, appreciate it, but I have one from a long time ago I can use for that.

    Jfast,

    Thanks for the troubleshooting sequence. I will check all of those things. What has me dumfounded is that the car worked when it was put on the ramps to put the DR750s in and I had the battery out the whole time, so I cant understand what could have broken or that I would have touched to make it not work. Those angle sensors are as old as the car and have 130k miles on them. The stock ECU was good when I pulled it out a couple years ago. I was hoping it was something stupid and I would realize it and that would be it, but after I looked at the obvious stuff, it got me worried since i have enver been in this spot with this car before

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    Forum User Feedback Score 0 HellBringer's Avatar
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    You may have already considered this, but were you using high impedance injectors with the AEM? If so, you'll need to reinstall/reconnect the OEM injector resistor box for the stock low impedance injectors.

    1993.5 Supra TT 6sp Hardtop -- old school 74MM setup: 10.4 @ 138MPH 1/2 mile - 166MPH - new setup #'s soon! [Previously 468WHP & 11.3 @ 125MPH stock twins]
    1994 Supra TT 6sp -- 11.8 @ 118MPH basic BPU
    1999 3000GT VR-4 -- 12.5 @ 108MPH 100% stock w/ Chromed ECU tune
    2003 Denali XL -- Grocery Getter & Tow Rig -- Runs 13's! (mpg)
    Formerly:
    1994 Supra 6sp - 72mm, VPC, stock longblock -- 722WHP & 10.36 @ 139.5MPH
    1993 Stealth RT/TT; 2003 Corvette Z06; 1997 3000GT VR-4; 2002 Corvette Z06;
    1999 3000GT; 1992 Stealth RT/TT; 1993.5 Supra TT; 1993 3000GT; 1992 3000GT VR-4;
    1998 Trans AM WS6; 1992 Talon TSi; 1993 3000GT VR-4; and many others..

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    Thanks HB but no, I was using low impedance injectors with the resistor pack like stock. I figured it out though just now. I noticed the cam sensor plug was unplugged. I forgot when I was pulling the intercooler pipes and the CF cam covers that I had popped off the plugs just to adjust the cover. I plugged them back in and thought doh!! stupid me and then it still did not start, but I got fuel!! I checked and no spark. The coil pack plug harness had popped back off when I installed it with the DLI harness attached. It started in a momentary crank and purred away. I forgot how nice the car starts stock and not running the AEM. Usually it cranks for a few seconds with the AEM. Now I got to find a few bolts I dropped, get it to an inspection station and reverse the mods LOL! I knew it would be a good day because my new BATTLESHIP plates came in the mail! I am going to get my methanol boxes mounted to a plate and zip tie it to the windshield water bottle. I hope theres enough room down there because I dont know where else to pount the controller and the flow safe module.

    Thanks everybody! I guess in my old age, I am getting a bit careless. I cant wait to get this car to Pampena for some tuning

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