FI issues?

yousaidpoo · 08-05-2004, 04:53 PM

ok. here's the deal.

car is a 1974 1.8L stock with L-jet

when i go to start the car, the fuel pump doesnt run for a second like its supposed to before the car starts to crank, but if i manually open the air intake sensor, the pump will begin to run. I'm assuming this is just a relay issue.

The big problem is the car is VERY difficult to start, and once it gets running, i have to really pump the throttle to get it to rev at all. usually if i just floor the gas pedal it will either do nothing or kill the engine. also, the few times i have gotten the engine to rev, it backfires. I just adjusted the valves, put a new fuel pump in, and put a new thermotime switch in.

Is all of this caused by the relay issue, or do i have bigger ghosts to track down?

thanks

jim

mike mueller · 08-05-2004, 05:42 PM

Quote:

when i go to start the car, the fuel pump doesnt run for a second like its supposed to before the car starts to crank, but if i manually open the air intake sensor, the pump will begin to run. I'm assuming this is just a relay issue

nope, that's the way the L-Jet supposed to work

with the key on, and the movement of air past the flapper, the dual relay energizes.....one relay turns on the fuel pump, the other relay gives 12v to the injectors.....

sounds like you have a major vaccum leak

Clay Perrine · 08-06-2004, 07:35 AM

Quote:

Originally posted by mike mueller
nope, that's the way the L-Jet supposed to work

with the key on, and the movement of air past the flapper, the dual relay energizes.....one relay turns on the fuel pump, the other relay gives 12v to the injectors.....

sounds like you have a major vaccum leak

Mike, you are close, but no cigar.. ;-)

there is a Yellow wire in the engine wiring harness on an L-jet system that comes out of the harness at the 12 pin connector end, and connets to the right rear connector in the 4 pin plug at the left rear of the relay board. The other end of this yellow wire connects to the double relay. When the engine is cranked, the fuel pump is energized. If the wire is not there, then the car won't start. The cranking speed of the engine does not create enough air flow to pull the air flow meter off it's stop and engage the fuel pump. After the engine starts, the contacts in the Air flow meter keep the pump running.

If you look at the wiring diagram for the L-jet system:

You see the wire listed as connected on one end to "T4II" and on the other end to pin 86 of the double relay. Start by unhooking the heavy yellow wire at the starter. This should prevent the engine from cranking. Then turn the key to the start position and listen for the fuel pump to run. If it doesn't, unhook the yellow wire from the 4 pin connector in the relay board, and with the key on, feed it power. The fuel pump should run. If it doesn't then you need to check it at the double relay end. Find where the yellow wire goes into the double relay (pin 86) and feed it power. The fuel pump should run. If it doesn't, hook the wire back to the relay board and connect a test light to pin 86 on the double relay. Then turn the key to the start position and make sure the light lights. If it does, replace the double relay.

BEWARE, there are some double relays out there for VWs that have the ground lead in a different location. It is physically interchangable, but the car will not run if it's installed. The difference in the part numbers is one digit, and the parts guys get them mixed up all the time. BTDT.

mike mueller · 08-06-2004, 10:27 AM

I still say I am correct, he's getting the car to run, so the yellow wire must be there

I just gave him the short version...basicly to let him know that it does not operate like a D-Jet equipped car........

Clay, could you post some L-Jet links for him to help with the troubleshooting? I cannot seem to find my bookmarks for L-Jet fuel injection............

Alfred1 · 08-06-2004, 10:36 AM

This L-Jet Troubleshooting Guide might help you find your problem.

Clay Perrine · 08-06-2004, 10:46 AM

Quote:

Originally posted by yousaidpoo
, but if i manually open the air intake sensor, the pump will begin to run.

The fact that you have to pump the gas, and you have backfires would indicate a problem with the air flow meter. False air (air that does not go through the air flow meter) is the leading cause of poor running on the L-Jet system. Carefully check the vacuum lines, and the hose routing on the system, including the big hose between the Air flow meter and the throttle body. It has a tendency to split between the pleats with old age.

Check the timing and the wiring mentioned above.

Mike, the flap and the start wire are 2 different circuits. Opening the flap does not do anything to the start circuit.

Tidybuoy · 08-06-2004, 01:37 PM

Jim,

I have a 1974 1.8 Fuel Injected 914 (L-Jet). I sounds like these guys have answered some of your question but here is my imput anyway.

1) the fuel pump dosen't run until the air meter moves (i.e., chrancing the engine or runnig the engine). Simply turning the key on will do nothing. I have tested my pump before by prying off the black plastic cap on the air meter & simply moving the meter. You can hear the pump run if you do this.

2) you mention that you replaced the thermo time switch. I beleive the purpose of this switch is to determine how long the cold start valve stays operating.

3) Have you replaced the head temp sensor. This is an $18 part and if it is bad - the car absolutely won't start.

4) is the car running rich (heavy exhaust smell)? it's possible that the cold start valve is sticking on. One way to test this is to unplug the cold start valve - which is probably not really needed during the warm season.

5) Vaccum Leaks. This is one of the most important issues with the 1.8. Simply stated, the air flow meter measures the air going into the engine and adjusts the fuel accordingly. If you have vaccum leaks, the engine is getting too much air but the computer dosen't know it and so the fuel is not adjusted to have the proper mixture.

there are many places to check for vaccum leaks: all vaccume hoses should be relatively new, intake manifold gaskets, dip stick in tight, oil cap gasket and gasket underneath the oil breather, air box bellows (remove & inspect for cracks - should be soft & pliable), fuel injector seals (both the large & small seals), central intake gaskets (the four hoses that are about 1.5 inches around and a couple of inches long, and the trrottle body gasket.

6) after you are sure that everything above is kosher, hopefully the car will run. if it does, check the timing & dwell.

7) lastly, make sure you hooked up the fuel lines in the correct order. It's easy to get them mixed up with the goofy 3 hose setup. On my car, I moved the fuel pump to the front (like on the 75/76 cars). When I did this I switched to the 75/76 style pump with one in & one out.

Hope this helps............................Vern

p.s. The is a really great book out there called "914 Tech Tips 700". this is the best book I have ever seen on the 914 and it has litterally answered all of my questions.

Tidybuoy · 08-06-2004, 03:52 PM

One more thing:

The ignition points are "more" criticle in the 1.8 L-Jet than in the 1.7 & 2.0 D-Jet. This is because the 1.8 ignition points control both the fuel injectors as well as the ignition spark.

The D-Jet engines have seperate trigger points for the injetors. So, make sure you have the points gapped correctly.

Alfred1 · 08-06-2004, 07:41 PM

Quote:

Originally posted by Tidybuoy

p.s. The is a really great book out there called "914 Tech Tips 700". this is the best book I have ever seen on the 914 and it has litterally answered all of my questions.

Well, I might have just ordered the Tech Tips book from AA. I went to their web site and added the booklet to my shopping cart and filled out all my billing info to see what the shipping would be and when I saw that it would be $12 - $17, I went back and deleted the booklet from my shopping cart before clicking on the final order confirmation icon. Now I see that I got an email from AA saying that my order has been processed. I just hope that Fedex doesn't charge a 20% brokerage fee at the border like UPS does.

jamcleod · jamcleod's Garage

i'm wondering if the hard starting could be caused by a faulty cold start valve.... it was not mentioned in all the tests... explain please?

yousaidpoo · 08-07-2004, 01:43 PM

i'm pretty sure that its not the cold start because its not just hard starting thats the problem. plus as far as the procedure in the manual goes for checking the cold start valve, its in working order

yousaidpoo · 08-07-2004, 04:39 PM

i checked the relay, and as far as i can tell, everything associated with it is working. there are no vacuum leaks, since i recently (a month ago) replaced every inch of hose in the car. i did notice, however, that my air intake sensor flap is sticking pretty badly. from what i understand, this would explain the problem, since its more or less stuck at idle.

is there any way to take the box apart to see if i can figure out how to get it "unstuck"?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Well, you can take the plastic cover off the top... That won't completely dismantle the AFM, but it may give you access to one of the pivot points. You may be able to clean it up and lube it that way.

The flap in the AFM may also be warped, causing it to stick. That is a known failure mode for them, and it is usually caused by a big backfire.

--DD

yousaidpoo · 08-07-2004, 06:36 PM

yea, i was planning on replacing it anyways. would that be a likely culprit for these problems?

jamcleod · jamcleod's Garage

maybe you could try "sticking" the AF vane open the next time you try starting the car. the vane needs to be open to run the fuel pump as was mentioned earlier (by clay?), and to run, it definately would need to be able to move freely.

to stick the vane open, maybe you could remove the air cleaner assembly. then you could access the vane....

i hope you continue to try to revive the L-jet FI system...

Clay Perrine · 08-09-2004, 03:29 AM

If the AFM is sticking, it's bad. There are no servicable parts there. I have a stack of AFM cores at home with sitcking flaps. Like Dave said, it's usually caused by a backfire. Chunk it in the trash and get one that is remanufactured. Then don't open up the plastic cover! They are set to work correctly with the injection, and you will not gain anything by tampering with the insides.

Will98D · 08-10-2004, 03:07 PM

Is this behavior new or has it done this for a while? If you can get the car running and warm it up, does it run OK? If you haven't done a full tune-up lately I'd start with that. It could be points/cond, timing, lots of things. If it runs OK once warm, it could be your aux air valve which should be open at cold start and closes with heat, but it could be stuck shut. This causes you to push on the throttle and when the engine is cold I'm not surprised you get a backfire. Also, I believe the cold start valve only works below ~32F, so you likely can rule that out unless it's leaking, in which case unplugging it won't help anyhow. Also pinch off the line going from the Decel Valve to the intake until you get this sorted out, then you can see if it's any good later. Good luck.

yousaidpoo · 08-12-2004, 04:48 PM

ok. got a new afm and put it in. i got the car to start and idle by checking/tightening/whatever all the hoses and whatnot. the idle speed is almost right at 500 rpm, and messing with the idler screw doesnt do anything. it will also occasionally jump to about 600 for a second or so. I'm thinking i dont have spark to a cylinder. i got a new distributor rotor/cap tonight and will put it on tomorrow if i have time.

if i hold the pedal to the floor, some of the time the engine will rev up, but not very high, and as soon as i let off, it will backfire.

the idle hunting problems sounds like it should be a vacuum leak, but i have checked everywhere, with the only exception being the hoses leading from the air intake distributor to the intake runners. could that be causing a problem

tomorrow i will put the new rotor/cap/spark plugs in asap and post an update.

Kenny Powell · 08-12-2004, 10:14 PM

I see in your very first post that you adjusted the valves(Recheck them).....I know by experience that this can cause your symtoms

Clay Perrine · 08-13-2004, 03:38 AM

The easy way to check which cyliinder is the problem is to unplug the injector leads one at a time. The one that does not cause an RPM drop is not firing. Then check the spark plug, the valves and make sure the injector is spraying fuel. I have seen where bad gas can clog the inlet screen in the injector.