Hi folks, hope everyone had a good weekend. I need to roll up my sleeves and dig into a new '75 DJet car to get it sorted out but have a quick question on the fuel pump relay behavior.

When I turn the key I can hear the fuel pump energize briefly and then the pump runs once started (and then dies). If the pump energizes and then runs briefly that suggests to me the fuel pump relay is good.

I'll swap in the the headlight relay just to make sure (since the headlights work fine so that relay must be good), but I wanted to check that my logic here is sound.

Thanks!

Good plan

Good morning Mark, thanks for the reply and confirmation.

Swapped in a known the be good replay and I’m getting the same behavior. The pump sounds labored so that is my next point of investigation.

Yup- that's how it's supposed to work. It should shut off after 1-2 seconds if the engine isn't running.

Sounds like the relay and pump is working fine.

The relay is energized in three conditions:

- "ECU" briefly energizes it when you turn on the key. That's to ensure you have fuel pressure. This is done via grounding the T4b-III wire.

- The pump is energized directly (bypassing the relay) when the key is in the start position, that's to ensure it's running during the start cycle. This is done via the T12-12 wire from the starter solenoid.

- The relay is energized by the ECU when it detects ignition (distributor or coil?) firing. This is to ensure the fuel pump is not running when the engine is not running. This is done via grounding the T4b-III wire as well.

You hear it during key cycle, so we know that part works and the ECU is sending the relay a ground signal.

You say the car starts and runs briefly, that implies it's working during the start cycle, supporting that the wire from the starter is good.

However, since it dies after start, that implies that maybe the ECU is not keeping it running? Or, maybe the ECU signal is not actually working and you're actually starting the car on the residual pressure from the start cycle?

I'd suggest jumping the fuel pump relay so that the pump is working all the time (jump terminal 30 directly to 87) and assess if that works.

If it does run that way, then I think that points to the T4b-III wire and/or the ECU not grounding the relay.

If it does not run...well, then I'm not clear the problem is with the fuel pump and/or its controls.

And...go!

*All these wires came from looking at a wiring diagram on a teensy phone, so I reserve judgement to be wrong on that detail. Please review the wiring diagram carefully!

Thanks for the confirmation and additional background, very helpful. I will try jumping those pins and see what happens.

So the pump runs continuously and it will briefly fire, I believe off the cold injector, and then run and stumble for a bit and then die. It doesn’t appear that there’s adequate fuel flow to keep it running or the main injectors aren’t firing properly.

I’m going to see if there’s anything obviously wrong with the fuel pump and make sure I’ve got good flow with the filter and get a fresh filter on it before checking fuel pressure.

Time to get methodical....

good idea, if you can get a generic pressure gauge in line you can see if its maintaining pressure or not,- the last time i had this happen exactly like you are seeing it was
a hose kinked under the tank so flow as not enought to maintain running, could also be a blocked screen in the tank or filter. or pump going on you, but i dont think its your board.

I did just go thru another episode a month ago and it would run, then die, so in that situation , my board had an intermittent short under the main power relay.
did you recently pull the tank and put it back in? its fairly common to have that line get kinked.

Phil

Do it.

Probably not? Unless that system isn't working correctly. Remember, that cold start system only fires with the key in the start position and with the thermoswitch grounding the valve, which only closes the circuit below about 32F. So if you're above ~32F (and I presume you are) then the CSV should not be firing at all.

I'm kinda leaning more toward the MPS. It reminds me a lot of the symptoms I had when my diaphragm was bustificated. It would fire and die, and *maybe* I could keep it running with a boot of throttle pedal. And to make that diagnosis worse, it would hold a vacuum...but when Tangerine pulled it apart it was clearly damaged.

But..."time to get methodical."

good point could be this too. so Greg, if it holds vac but the diaphragm is damaged if he checks the inductance under vac the values will not be correct and this should indicate a bad diaphragm, correct?

Phil

MPS most likely. Need to test it.

The fuel pump is making a wheezing sound, it may not be the case but it sounds like it’s struggling to get fuel flow. Tank has enough fresh fuel, and it looks like someone’s been in there to replace one of the fuel lines which could be a good or a bad thing depending on anything else they did.

For a 1975 would you guys recommend pulling the gas tank up a bit so I can have better access to see what’s going on in there or remove the steering rack cover and gain access from the bottom of the car?

I believe I have a known to be good MPS that I bought from you (Rob), will grab that since it’s easy to swap out.

Thanks!

Oh...wow yea I did sell you one. Thought I sold that with my 73 but maybe I did sell it to you. Jeff Bowlsby rebuilt that one and it was meant to go into a new 2056 I was working on. Then a guy walked up and wanted to buy the car.

How time flies.

I think if it runs and then stops then most likely the fuel system. I had a symtom like this once and it was a kinked fueld line underneath the rack. This was another reason I didn't like the fuel pump up front but that's just my opinion. Good luck Tom.

OK - update: swapped in the new MPS from Ron and it ran a bit longer then died. Upon restart it ran for a bit less time and then died. 3rd start it labored then died.

This well could be misplaced but as of right now my guess is that the car has a construction in the fuel line that after sitting doesn’t block flow but then as the demands placed on it it constricts and then won’t release until all the vacuum is out of the system.

Time to pull the tank / or cover plate I think.

Thanks gentlemen, appreciate the help.

Hmmmmmm - that looks pinched, bit hard to see so I put some yellow arrows.

Wonder if that is collapsing?

Click to view attachment

Just re-routed the lines a bit to make sure nothing was kinked and she started and ran fine.

Looks like bad line routing and poor quality / old / wrong spec fuel line was the cause.

Once that is all replaced with new and correct bits will run it and then "try" the old MPS to see if that was contributing.

Fingers crossed.

I've fought this fight. Thus was my problem too. I'd put money that this is the smoking gun.

I fear the tank lines worse than the airbox.

I *HATE* working on the tank lines. I keep threatening to cut that area out and replace it with a Dzus-fastened access plate.

One thing I did last time was replace the hose bends with bent stainless tubing, using the hose just for coupling. Not too hard with a brake line/pipe bender/flare tool and you don't have to worry about those hoses kinking.

I hear you,guys, living it right now.

Good news: got that old hose out and it turns out it was not even fuel line, it looks like it was heater hose!

Bad news: It went from starting and running much better to dying on me halfway around the block. I was able to get it started again and limp home so either I still got a kink in there somewhere or there’s another issue I need to run down.

There were some off-brand fuel pump in there so I replaced it with a Bosch unit.

That's a great idea. The location of the hoses without easy access is such a PITA.

I recently went through this on my 72.
The front fuel line from the tank kept kinking.

After several attempts that all failed over time, I went and got a screen door springs from ACE hardware cut it to length and stuffed it inside the fuel hose from the fuel tank to the tunnel line.

The hoses can not collapse or kink anymore.

Jim

Also ran into a problem with fuel line kinking, It would run and idle but as soon as I put a load on the engine it would begin to loose power, sometimes dying, immediate restart though.

I solved it by reducing the length of the hose ( I had it looped around under the tank)

And putting stainless braided hose I had from the motorcycle on, that won't kink.

Had a fuel pressure gauge on and could watch the pressure drop when it would loose power.

Check thread below, there is also a video of the fuel pressure gauge in there.

http://www.914world.com/bbs2/index.php?sho...=352435&hl=

Thanks for the ideas, think I have a feed line kink to resolve now.

This probably isn’t helping anything....


Click to view attachment

Well re-routing and shortening that line, as well as the other larger line, did the trick.

@914_teener that MPS you provided is working great.

Lots of deferred maintenance to do but with everyone's help we have another 1975 914 back on the road.

@mepstein - per your coaching some years ago I'm going to leave this on fuel injected, it does make for nice driving car.

Thanks again for all of the help!

I looped the fuel lines back and forth under the tank leaving enough hose to be able to pull the tank completely out w/o removing hoses. Nice long loops with no kinks.

I like that.

This is exactely what I did. Happened twice.

Sounds like you got it sorted Tom.