75 1.8 L-Jet Fuel pump starting problem...

[rockaria]

Maybe you all can help.

I have a 1975 1.8 L-JET that works very nice and runs great. Today was the first day I took it to work and it sat in the 100 degree sun for 4 hours. It started perfectly last night, and this morning. But at lunch it would not start.

I traced the problem to the Fuel pump not running when the starter is cranking. I was able to take off the cover to the Airflow meter and noticed it did not move when cranking. When I did move it by hand while cranking the car started right up and ran perfectly all the way home.

So all that is wrong is this fuel pump/airflow switch not getting the power it needs or whatever to operate. But once it is started the fuel pump and FI system work flawlessly.

Now before I go at it, does anyone have any clues to help out. I would like to just go in and fix it and be done without a lot of mesing around. I will check power at the fuse, and power at the relay. But since it works fine when started, these should be working, right? I believe the direct hot sunlight has something to do with it, but what?

Any other clues?

Thanks,

[Kenny Powell]

chris, from what you described it sounds like the air flow meter. I was going to suggest some other things but, you mentioned when you moved the meter inside it runs great. I've also been cautioned by reputable mechanics about taking that cap off and playing around inside there.



75' 2.0 w Ljet

[rockaria]

I move it just enough for the contacts to touch and it starts right up. Then I put the cap back on and it runs perfectly. This would be the same thing if I took off the air filter cover and pushed in the flap, just easier. Nothing else has been touched with in the top part. It looks perfect, and like I said this is the first time it happened and the only diff was the 4 hours of direct sunlight.

[dave blackburn]

Hey. Your airflow meter turns on the fuel pump when it moves from the engine vacume. If you move it by hand you should hear the fuel pump running. If the air flow meter does not move when cranking I would look for some intermitant vacume leaks, also check the air bypass valve. I would also check that the air flow meter is moving freely and its not all gummed up. It is ok to use wd 40 on it, but I would reccomend just some light oil on the bearings/bushings and just wipe the exess off of the wiper contact strip. You can also use some fine 200 grit sand paper to clean the fuel pump switch contacts in the air flow meter box. Hope this helps. Dave

[rockaria]

Could it be the dual relay?

When I crank it the flap in the AFM do not move at all. They are clean and move freely. Once started the flap on the AFM works perfectly, Well it seems to, the car runs fine and purrs like it always did.

I don't think the vacume has to do with a 75 L-Jet closing the pump points when cranking. I think it is an electric thing. But I will check.

Thanks,

[Serge914]

Chris I had the same problem on my 74 1.8L. I would push the flap with a long screwdriver and it would start. I am not sure how I did fix it but I replaced all the vacuum hoses and the starter in the same period of time and the problem did disappear. I noticed the new starter was cranking the engine faster, wich is probably creating a bigger vacuum. Good luck.

[scotty914]

you do not need air flow to turn on the fuel pump relay ( in the double relay pack not on the reg board ) there should be a yellow wire on the reg board ( four pins rear drivers side of board ) that is on the passenger side rear pin, it feeds the crank feed to the relay to turn the pump on when cranking

then when the motor starts the flap takes over, i would check this for signal when cranking by pulling the point wire fron the coil and crank the motor to see if the pumps starts or better ( alot quieter ) pull the yellow wire off of the starter and crank away ( no crank really but all the proper power to everywhere but starter ) if you dont get this to work right you are asking a lot of the starter to draw enough air

back to another replie DO NOT DO NOT DO NOT DO NOT ( reread the last 8 words 3 times ) use wd40 in the airflow electronics it breaks down the carbon tracks, i did this on my old one and it wiped the carbon off in 2 weeks rinse with alcohol then use a light grease on the pivot point

to the orignal problem i would bet it was just simply the flap stuck to the stop inside the air flow meter from the heat, i would pull the air filter and check the stop it has a peice of rubber on it it might be bad, covered in gunk, oil or just old

tip for all l jet users ... put a short wire tail off of one of the screws that holds the reg board in place with a female spade connector on it and keep a relay in the feul pump spot, first it gives you a spare relay if you need it and two you can put the spade connector on the drivers side front pin (of the four on the rear drivers side of the reg board ) and the fuel pump will turn on with the ignition .... useful for testing fuel pump, pressure etc or to get you home when the fuel pump wont run otherwise

this is how you get the fuel pump to run for carb conversions too

[rockaria]

I fixed it! I checked everything. The relay, Airflow meter, everything. All components checked out. So I started to check the lines in the Harness. It seems the Reg box (Drivers side rear engine compartment) T12 post 12 had come apart and was not connecting (The wire came lose from the prong in the plug 12 of 12 prong connector, preventing the 88d 12v to get back to the fuel pump.) I soldered it back onto the post put it back in and it started and runs better than ever before.

The relay takes 12v from the starter (Yellow wire from the T4-II prong on the reg box to prong 86a on the double relay) and sends it back down the line to the fuel pump (88d on the double relay through a black wire to the reg box post T12-12 the directly to the Fuel pump) when the starter is running.

The air flow meter or the FI Brain has absolutely Nothing to do with the fuel pump when starting and it seems that vacume or airflow does not either. The Double relay bypasses the AFM fuel pump switch completely when the starter is engaged and starts the pump directly. Cool!

The absollute BEST resource on the Net for L-JET diagnostics and understanding that I have found is the "Volkswagen Technical Articles" at:

http://type2.com/bartnik/tech1.htm

the L-Jet stuff is at the bottom of the page and is quite complete. It is written for a normal person to understand and has great pictures. As well it has full "Here is what the part is", "How the Part Works", and "How to test the part."

Very Cool! They saved me a lot of time and wasted money.

I hope this helps someone in the future,