75 1.8 garage find won't start Options

[ahdoman]

Also check the 2 fuses on the relay panel. I believe one of those is for the power to the relay's and the other for the fuel pump? Since they are exposed they get corroded very easily.

[ClayPerrine]

Clay...info I got was from a Porsche mechanic who helped me get my 75 l-jet sorted. The AFM completed the circuit (according to him) and it needs to open just enough to allow the pump to run (relays, afm etc are all in the loop). He was dead on as the test we did with him there was open it alittle and behold..the pump started. His explanation was porsche did this so as not to have fuel being dumped in without air. I'm no expert here but this came right from a Porsche mechanic and he demonstrated the fuel pump not running when cranking and the flap close...and the fuel pump ran when opening it slightly. I saw it with my own eyes. Maybe the 75's are different but that is what I saw.

I have been doing this (and living with a L-Jet equipped 914) for 24 years, and I had factory training from VW on the L-Jet system. Your mechanic is partially right. The air flow through the air flow meter should trigger the fuel pump. But when you are trying to start the car, there is not enough air to consistently trigger the fuel pump. So they have the circuit tied to the starter circuit that causes the pump to run when the engine is cranking. It does not run when the key is in the on position, only when it is in the start position. If you don't believe me, take the yellow wire off your starter and see if the pump runs when the key is turned to the start position.

Also check the 2 fuses on the relay panel. I believe one of those is for the power to the relay's and the other for the fuel pump? Since they are exposed they get corroded very easily.

The fuses on the relay board are not used for the injection on an L-Jet car. You do not need either the fuses or the relays on the relay board.

[computers4kids]

Clay...info I got was from a Porsche mechanic who helped me get my 75 l-jet sorted. The AFM completed the circuit (according to him) and it needs to open just enough to allow the pump to run (relays, afm etc are all in the loop). He was dead on as the test we did with him there was open it alittle and behold..the pump started. His explanation was porsche did this so as not to have fuel being dumped in without air. I'm no expert here but this came right from a Porsche mechanic and he demonstrated the fuel pump not running when cranking and the flap close...and the fuel pump ran when opening it slightly. I saw it with my own eyes. Maybe the 75's are different but that is what I saw.

I have been doing this (and living with a L-Jet equipped 914) for 24 years, and I had factory training from VW on the L-Jet system. Your mechanic is partially right. The air flow through the air flow meter should trigger the fuel pump. But when you are trying to start the car, there is not enough air to consistently trigger the fuel pump. So they have the circuit tied to the starter circuit that causes the pump to run when the engine is cranking. It does not run when the key is in the on position, only when it is in the start position. If you don't believe me, take the yellow wire off your starter and see if the pump runs when the key is turned to the start position.

Also check the 2 fuses on the relay panel. I believe one of those is for the power to the relay's and the other for the fuel pump? Since they are exposed they get corroded very easily.

The fuses on the relay board are not used for the injection on an L-Jet car. You do not need either the fuses or the relays on the relay board.

Are you sure about the relays on the board? I too had an Ljet that had been parked for a year because it wouldn't start. I went ahead and cleaned the blue 25 amp fuse closest to the firewall (didn't help), the other fuse is for the rear glass defogger if equipped.

However, the last relay (closest to the firewall) is part of the equation. When I changed mine out with a known good one the car fired to life instantly.

[jhelgesen]

Does someone have this picture for a 75 1.8 car? Or can tell me the differences?

(IMG:http://www.914world.com/bbs2/uploads/post-994-1260458645.jpg)

[type47]

The factory workshop manual shows 3 relay boards, the last one for a 73. I would then guess that 73-76 are the same.

[ClayPerrine]

Clay...info I got was from a Porsche mechanic who helped me get my 75 l-jet sorted. The AFM completed the circuit (according to him) and it needs to open just enough to allow the pump to run (relays, afm etc are all in the loop). He was dead on as the test we did with him there was open it alittle and behold..the pump started. His explanation was porsche did this so as not to have fuel being dumped in without air. I'm no expert here but this came right from a Porsche mechanic and he demonstrated the fuel pump not running when cranking and the flap close...and the fuel pump ran when opening it slightly. I saw it with my own eyes. Maybe the 75's are different but that is what I saw.

I have been doing this (and living with a L-Jet equipped 914) for 24 years, and I had factory training from VW on the L-Jet system. Your mechanic is partially right. The air flow through the air flow meter should trigger the fuel pump. But when you are trying to start the car, there is not enough air to consistently trigger the fuel pump. So they have the circuit tied to the starter circuit that causes the pump to run when the engine is cranking. It does not run when the key is in the on position, only when it is in the start position. If you don't believe me, take the yellow wire off your starter and see if the pump runs when the key is turned to the start position.

Also check the 2 fuses on the relay panel. I believe one of those is for the power to the relay's and the other for the fuel pump? Since they are exposed they get corroded very easily.

The fuses on the relay board are not used for the injection on an L-Jet car. You do not need either the fuses or the relays on the relay board.

Are you sure about the relays on the board? I too had an Ljet that had been parked for a year because it wouldn't start. I went ahead and cleaned the blue 25 amp fuse closest to the firewall (didn't help), the other fuse is for the rear glass defogger if equipped.

However, the last relay (closest to the firewall) is part of the equation. When I changed mine out with a known good one the car fired to life instantly.

Sounds like pure coincidence to me.

I am 100% positive about this. Betty's 914 has not had a relay on the relay board for years. She doesn't have a heater hooked up, no heated rear window, and no D-Jet. And it runs just fine.

The relay boards for all years of 914/4 cars were functionally identical. I assume there were manufacturing changes because there are no electrical changes to the board.

[computers4kids]

My 74 Ljet has only has two relays and one does run the heater. Clay I know you know the in and outs of Ljet very well, but I'm pretty sure my L-jet has to have at least the one relay to startup and run. You have me curious now. I'll have to pull my two relays and see what happens. Even though when I cleaned the blue 25 amp the car still just cranked and cranked, perhaps it was a delay re-action. It's been a long time since I've had an L-Jet.

[ClayPerrine]

My 74 Ljet has only has two relays and one does run the heater. Clay I know you know the in and outs of Ljet very well, but I'm pretty sure my L-jet has to have at least the one relay to startup and run. You have me curious now. I'll have to pull my two relays and see what happens. Even though when I cleaned the blue 25 amp the car still just cranked and cranked, perhaps it was a delay re-action. It's been a long time since I've had an L-Jet.

You shouldn't need the fuse either. All of the power for the L-jet system comes from the power feed wire that runs between the double relay and the battery.

[zonedoubt]

(IMG:style_emoticons/default/agree.gif)

To understand how the double relay works, read this.

[jhelgesen]

Super!

Thanks,

[davesprinkle]

You shouldn't need the fuse either. All of the power for the L-jet system comes from the power feed wire that runs between the double relay and the battery.

Clay is correct here. The Ljet system pulls its power directly from the positive lead of the battery, bypassing the fuse on the relay board.

The Ljet wiring is a poor design for a number of reasons; the main one being: IT HAS NO FUSE. I strongly recommend adding an in-line fuse to the double-relay battery supply lead.

[ClayPerrine]

You shouldn't need the fuse either. All of the power for the L-jet system comes from the power feed wire that runs between the double relay and the battery.

Clay is correct here. The Ljet system pulls its power directly from the positive lead of the battery, bypassing the fuse on the relay board.

The Ljet wiring is a poor design for a number of reasons; the main one being: IT HAS NO FUSE. I strongly recommend adding an in-line fuse to the double-relay battery supply lead.

I just replaced the loop on the end of the wire with a fusible link that already had the loop on the end. Now I don't worry so much. (IMG:style_emoticons/default/biggrin.gif)

[jhelgesen]

Didn't make it past step one. No pump running when I move the vane in the AFM.

I tested the relay best I could. I could make both coils click, fuel pump contacts had continuity.

I do have 12v at the resistors.

Wire on the advance plate is in good shape.

[r_towle]

you stated that the fuel pump runs when you run it off jumpers, right?

The main coil pack should have 12vdc at the middle pole.
The fuel pump relay is in a small unit next to the tubular ones.
Does that one function?

Rich

[ClayPerrine]

Didn't make it past step one. No pump running when I move the vane in the AFM.

I tested the relay best I could. I could make both coils click, fuel pump contacts had continuity.

I do have 12v at the resistors.

Wire on the advance plate is in good shape.

Sounds like the contacts on the double relay are bad. Do you have another you can try?

[jhelgesen]

Tested power at the pump this morning. I got power to the pump while attempting to start, and it was going through the relay. (should have also checked the afm at the same time, but was trying to get out the door to the office, I'll check that again tonight to see if I just couldn't hear it)

12v was also at the center pole of the resistor pack.

I can start to smell fuel at the tail pipe.

A change of spark plugs is in order also.

[Dave_Darling]

My 74 Ljet has only has two relays and one does run the heater. Clay I know you know the in and outs of Ljet very well, but I'm pretty sure my L-jet has to have at least the one relay to startup and run.

As far as I can tell from wiring diagrams, from manuals, and from working on my own 1.8, none of the relays on the relay board are needed for an L-jet car to run. Just for the heater blower and the rear defogger.

(In fact, that was a MUSR tech quiz question one year.)

--DD

[jhelgesen]

Still trying to start the motor without success.

I know I have mis-matched injectors right this second, but was going to fix that soon.

Right now I have 3 from a 912-e and one of the original 1.8's. I have a nice set of 1.7's on the shelf....

Trying to understand from what I've been reading, are L jet and D jet injectors not compatible? I saw the flow rates the same for the 1.7's vs the 1.8's, so I thought....

(BTW, I'd trade the 1.7's for 1.8's if someone was interested)

[7275914911]

Still trying to start the motor without success.

I know I have mis-matched injectors right this second, but was going to fix that soon.

Right now I have 3 from a 912-e and one of the original 1.8's. I have a nice set of 1.7's on the shelf....

Trying to understand from what I've been reading, are L jet and D jet injectors not compatible? I saw the flow rates the same for the 1.7's vs the 1.8's, so I thought....

(BTW, I'd trade the 1.7's for 1.8's if someone was interested)

If I remember pulse rates are different so not interchangable 1.7 to 1.8.....it's a Djet vs Ljet thing. I bought NOS Ljet injectors from AA last year for around 55 each when chasing down a rich running problem I was having (see below that injectors was not my problem). I have the injectors that I replaced that are very usable as is and would be in great shape if cleaned.

There are others smarter than me that will chime back in I'm sure.

My experiance with 75 1.8 Ljet Relay talk above is this. When I had Relay's in my relay board FP ran all the time. It was in a 72 body so I assume earlier relay board. FP was running so much I was thinning out my oil because so much gas was getting by rings....ouch (and that 1.8 is still strong as an OX).

Good Luck

Ken

[jhelgesen]

This morning, I broke down and sucked the smidgen of gas out of the tank and replaced it with 4 gallons of nice fresh super unleaded. Checked all was still hooked up and turned the key.

After several attempts I got a pop. Kept trying and she fired.....

IT IS.....ALIVE!!!!!

She only ran a few seconds, so I tried again with the same results. Fuel pump runs when starting, but does not continue. I'm leaning toward the AFM, should have a buddy bringing one over tomorrow to test the theory.