'74 1.8L LJet/fuel pump, Fuel Pump not staying on Options

[ndfrigi]

Interesting......just makes it harder for us novices to try to trouble shoot.
Picking up a loaner AFM this evening

Sorry again David that my AFM has 7 pins compare to your 6 pins. Hope you can find one with 6 pins or hoping also it’s not the AFM that you need.

[RKramden]

I will check ohms on AFM this weekend. If they don't check out, off to Pelican for a rebuild. If they do check out does that mean it's good or could there still be an issue with the signal when running? If it is good am I down to the ECU?...ouch!

[ClayPerrine]

I will check ohms on AFM this weekend. If they don't check out, off to Pelican for a rebuild. If they do check out does that mean it's good or could there still be an issue with the signal when running? If it is good am I down to the ECU?...ouch!

The ECUs rarely fail. It is either the L-Jet harness or the AFM. Maybe someone close to you has one you can use for testing.

I recently sold one to @Rob-O . He was having drivability issues, and the replacement AFM fixed it.

[RKramden]

I continuity tested all the wires from the ECU and they checked out
If there is someone out there with one to loan, that would be great, otherwise $260 from Pelican isn't the end of the world.

[Rob-O]

I will check ohms on AFM this weekend. If they don't check out, off to Pelican for a rebuild. If they do check out does that mean it's good or could there still be an issue with the signal when running? If it is good am I down to the ECU?...ouch!

The ECUs rarely fail. It is either the L-Jet harness or the AFM. Maybe someone close to you has one you can use for testing.

I recently sold one to @Rob-O . He was having drivability issues, and the replacement AFM fixed it.

Absolutely helped clear up some serious drivability issues.

[porschetub]

Are the wiper boards still being made by anybody ?,I seem to remember 914rubber had them but they were D-jet ones or are they the same?.
I noticed Fuel Injection Corp have L-jet AFM's rebuilt on ebay for $199 .

[Rob-O]

The only ‘wiper boards’ I know of that we’re being reproduced we’re those that go in the throttle bodies.

In a 1.7/2.0 D-Jet, that TB board is used to tell the ECU the load on the engine...or more simply, what position the TB is at. On the L-Jet, that board inside the AFM. The ‘wiper board’ on the L-Jet TB is only used to tell the ECU when it is at wide open throttle. None of the boards are interchangeable to my knowledge.

[Rob-O]

Forgot to add, I looked at Fuel Injection Corp’s offerings. I don’t believe that they replace that board. I think their work includes cleaning the board, checking wire continuity, checking the ‘barn door’ flap for binding, adjusting the tension and position of the wiper arm. essentially bringing the unit back to factory specs.

There is a document floating around the ‘Net (itinerant air cooled.net maybe???) where someone explains the adjustments. I’d take that information with a grain of salt. But the document helps explain what the AFM does and how it works.

Even if you go the rebuilt unit from FIC, you might want to use a portable O2 sensor to have the air bypass set correctly for your engine.

[Rob-O]

BTW, you’re welcome to my old AFM. It had been rebuilt and subsequently fiddled with by a PO. There is a decent shudder around 3000rpms but it should work fine for isolating your issue. Heck you could probably run it for a bit until you can get yours repaired/replaced. Just PM your address.

After reading the rest of this thread, I’d agree with Clay. AFM or the harness.

[RKramden]

SUCCESS---kind of
Ohm tested the AFM and was 290 between 6 & 9, and 170 Between 7 & 8 and 36 and 39 were infinite when closed and 0 when open....all per spec. Decided to check these same readings at the ECU plug and found the same (with the AFM plugged in) except between 7 & 8 when sometimes I would get an infinite reading. Started jiggling those two wires all the time watching the reading change from infinity to 170 (note that I had previously stripped the plastic sheathing off of the ECU wiring harness looking for possible breaks a while ago). Worked my way back to the AFM plug where the problem seemed to be coming from. I removed the rubber surround on the plug and found that I could move #7 in and out ever so slightly, and make the Ohms switch. I cut the plug off and crimped new individual connectors on, and viola!....It started and stayed on with all wires connected! Now it wants to die when I punch it, but I can get the RPMS up by feathering the peddle. I will replace the rubber hose between the AFM and the throttle body that just arrived and check for any other leaks......Any other suggestions?......how much tension or slack should there be in the throttle cable at the TB connection?

[ClayPerrine]

Now you know the harness is bad, so I suggest getting a Bowlsby replacement.

Bowlsby Wiring Harnesses

That and a new AFM hose should get you closer to running.

[RKramden]

Now you know the harness is bad, so I suggest getting a Bowlsby replacement.

Bowlsby Wiring Harnesses

That and a new AFM hose should get you closer to running.

It's on the list!