factory fuel injection install troubleshooting

[34mike]

I just retrofitted my carbed 302 over to fuel injection from a 89 mustang donor car I used the factory wiring harness and all components needed to convert my car over to F.I. , installed rail mounted fuel pump (45psi) and return line. A9l computer, etc... The problem I'm having now that i got the car running is it wont idle when you first start the car in the morning it idles fine after it is warm (180deg.) I checked the idle circuit and found a short so i ran a jumper wire and the idle bleed valve started showing a return voltage I thought I had found the problem but it is still there Forgot to mention the engine has a fordmotorsport B303 cam with .480 lift 280deg. duration My thought now is that when the computer is in open loop during the warm up time the cams duration is too long for the programed injector time open but I find that hard to believe because during war up the car should be running rich right? and during the warm up time once I get it started it wants to idle up to 1000rpm then down to 300rpm then back up and down.!!! what do you guys think this is?

[frdfandc]

The B cam is small enough not to give you any idle problems.

Your idle surge is a faulty IAC solenoid. Make sure you pick up a Motorcraft IAC solenoid. The aftermarket ones are junk.

[34mike]

Thanks for the help on the cam I hoped that was the case . As for the IAC I aready replaced it while I was tracing down the short in that circuit. It did the same thing with the new one as with the old so being the cheapster i am i put the old one back on since it didnt make any change How do i check the IAC valve to make sure it is working like it is suppost to. I am getting 13 volts in on the red wire and 10 volts out on the white/blk.strip. wire is there a way to check the valve to see if truly is working I tried taking it off the throttle body and looking at it to see it move with the key on ,no real results there , tried to start the car to see if it would open but with the IAC valve off there is a huge vaccume leak and couldnt get the motor to run so that really didnt work do you have and more suggestions .

[frdfandc]

Your voltage seems to be ok.

The VPWR circuit should be 10.5 volts or higher
The ISC-BPA signal from the PCM should vary between 3 volts and 11.5 volts with the engine running while slowly increasing and decreasing RPM.

Have you checked for any type of vacuum leaks??? Take some carb cleaner/gum cutter and spray around the intake, intake tube, mass air meter, and especially around the back side near the vacuum tree.

Since the donor equipment is from a 89 car I'm assuming its Mass Air. Just make sure all your basics are rechecked. Grounds, connectors, etc.

If you need further diagnostics head to your local Book Store and pick up this title:


How to Understand, Service and Modify Ford Fuel Injection & Electronic Engine Control
By Charles O. Probst, SAE.

[34mike]

Turns out guys it just needed more fuel pressure than the stock regulator could give during start up and warm up I put a adjustible regulator on it because I ran a test I took the air cleaner off and sprayed gas down the intake tube while I was starting it and the motor ran fine while I was spraying gas the minuite I stopped the motor stalled so my guess was that the motor just wasnt getting a rich enough mix to run cold with the 19lb. injectors and that B303 cams long duration. I cranked the pressure up and reinstalled the vaccume line, the car started right up and idled just fine cold. Hope this helps anyone else that is having this problem.

[Adam McLaughlin]

What is your fuel pressure set at? Should be 39 pis with the key on engine off, and somewhat less than that with the engine running and vacuum applied.

When the motor hunts for a desired idle speed, it is really playing with the timing, not so much the IAC operation.

You are welcome to visit EECTuning.org for more information. It's my second home. :o)

Adam

[34mike]

Wanted to update on this thread I found later that the problem came back so i replaced the Mass Airflow meter with a new one for a 89 5.0 and it smoothed right out, the old one was actually off a crownvic that had a 5.0 modular motor I was told it didnt matter as long as the plug matched WRONG!!!