Ultra rich at cold start???

[jameslleary]

Holley TBI have Adjustable Fuel Pressure Regulators? Try less fuel pressure. Was the Holley TBI on the engine before the rebuild?

dave w

No, he had the stock rochester and all sensors have been replaced 3 times trying to track down this issue. fuel pressure is currently at 12 psi.
Mark, all he has is an ALDL cable, and TPRT....is there a way to just log without diag. mode?

[EagleMark]

I don't know how he got in Diagnostic Mode? ALDL mode is when 10K is applied which is the mistake people usually make. Diagnostic mode was IIRC 3.9k and I don't even remember what for? Or is diagnostic mode when A and B are crossed?

Does his CEL work correctly?

1project2 many may know what Diagnostic mode is or how it got there?

[1project2many]

Diagnostic mode is 10K across A-B. 3.9K enables Backup fuel / LHM and Field Service is enabled when A-B are shorted. Once upon a time the 7747 wouldn't even give out data unless you were in diag mode. Some of the cables come with DIAG mode automatically enabled.

[EagleMark]

Thanks 1project2many!

Well then he has the 10K on cable, should be open. But there might be more wrong because I have seen other data from people with ALDL mode enabled with 10k?

[jameslleary]

crapola...should I have him pull A and/or B out of the ALDL?

[EagleMark]

? I just plug my cable in and don't use the jumper for 10k. Or use my AutoProm and don't use 10k switch. What is he using for cable?

[EagleMark]

Even if he gets the Diagnostic Mode off I don't think data is going to help with vacuum that low at idle... something mechanical is wrong!

[jameslleary]

yeah, we are looking at everything. I have him adding a heated o2 for long tubes. then take the 10 k chip out.

[EagleMark]

With vacuum that low, data or heated O2 is moot.

[jameslleary]

Ok, so he sent me a log, I told him to unplug the cts, reading drops to -40* and he apsaid it started running real good.
Why would it straighten up at -40, and run pig rich at 70*? Ideas?

[EagleMark]

Hard to tell what a cold motor is doing open loop, but as you know going to -40C is adding fuel! What I saw when he added fuel was vacuum go up?

EDIT: Diagnostic mode still on?