If the pump can't get it up to pressure immediately, then that might be your problem. At least with the pumps I use, I'm used to an immediate jump to full pressure, and I'd be concerned that any pump that couldn't do that would be able to give good fuel pressure much past idle. What part of Germany are you in? I spent a few years there in the Ansbach and Schweinfurt areas.
1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
1975 280Z, TBI 350, 700R4
1953 M-38A1, TBI Buick 231
1951 Ford Panel, 5.3 with 4L80E
The Airtex pump is designed for the TBI systems, but maybe I got a bad one. I'll watch the pressure gauge closely and report back asap. How much pressure can the regulator take without getting damaged? I might as well think bigger in case I need a replacement pump...Originally Posted by fastacton
I live in Berlin now, but I went to college in Würzburg, so I know the Schweinfurt area. A nice part of the country...
Reporting back - I fixed the fuel pressure problem. The car now runs mostly fine. There's only one and a half issue bugging me.
The half-issue is unstable idle in closed loop, I've seen tons of threads about this here so I guess I can tackle that on my own.
The biggie is the spark advance: I am trying to re-create my stock dizzy's advance map as a first step and the engine starts having ignition problems as soon as the advance crosses 30°. It's clearly rpm-independent: Wherever I set the advance map to cross 30°, the ignition starts having problems, I even blew my muffler with a violent backfire!
First, I thought I might have an arcing problem so I phased my dizzy correctly. Didn't change a thing. So I connected an engine tester and discovered something really weird:
Yep, somehow, each plug suddenly starts firing twice.
I then moved the P/N wires further away from the coil to rule out any interference from the discharge. Checked the signal with an oscilloscope, it's clean. The oscilloscope also tells me that the coil in fact is triggered two times per plug by the HEI module.
How's that possible? Bad HEI module? Bad ECU? I really need some pointers here...
Last edited by Dr_Grip; 06-20-2015 at 11:48 PM.
I would think it would be the module or distributor issue. The ECU doesn't tell the module how many times to fire, just how much advance is needed (as far as I understand things).
1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
1975 280Z, TBI 350, 700R4
1953 M-38A1, TBI Buick 231
1951 Ford Panel, 5.3 with 4L80E
Thank you for the quick reply, much appreciated!
That's what I think, too.
I've read on another forum that mounting the module too far away from the dizzy can cause issues, as well. What do you think about that?
EDIT: Here's the wiring. Module is located on the passenger side fender.
Last edited by Dr_Grip; 06-21-2015 at 11:24 AM.
I've only used HEI style distributors on my Ford builds, so your wiring setup is a bit different than what I'm used to. This is a good link for how things should be wired up(it's for megasquirt, but still applies):
http://www.megamanual.com/ms2/GM_7pinHEI.htm
1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
1975 280Z, TBI 350, 700R4
1953 M-38A1, TBI Buick 231
1951 Ford Panel, 5.3 with 4L80E
So you mounted the ECM on the intake manifold?
If so, stop the show and move the ECM to the interior. The '7747 is not designed for the underhood environment. The moisture, heat, vibration and other fumes/chemicals,/etc will cause you problems in time, if not very shortly.
It seems that the Ford dizzies don't have a solid enough signal to reliably trigger a GM ICM. It works, yes, but not as well as a GM reluctor does. I've seen a few solutions used, adapting a GM dizzy to the Ford, adapting a GM reluctor to a Ford dizzy. There could be an electronic solution as well, to improve the signal, using an amplifier, but a mechanical solution seems to be the best.
Are your wires between the dizzy and the ICM twisted? They should be. IIRC the recommended is 3 to 5 twists per inch. The twists help reduce the possibility of inducted noise interfering with the signal.
The man who says something is impossible, is usually interrupted by the man doing it.
Thank you for the link - but it's the manual I used anyways :)
Wait, how did you get this impression? :) Of course I didn't! It is - not ideally, I know - taped to the rear side of the driver's side fender for now. I'll rip the interior out for a rustproofing effort in a few weeks time and will move the ECM below the front bench then.
I'll keep an eye on that, thank you for the heads-up! Right now, my problem seems to be too many triggers, not too few, but it's good to know.
They aren't. I guess that's where my problems come from. I'll switch to shielded twisted cables on Tuesday and report back.
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