TheSamba.com :: View topic - No Fuel to Engine

Sat Nov 07, 2009 9:40 am

Greetings all - I am new to the forum and have been the happy owner of a 1977 Super Beetle (Triple White conv.) for a couple of months. I have replaced many components in the vehicle without too much trouble until my recent endeavour of replacing the fuel lines.

Basically, the smell of gasoline is rather strong, so I sought out to replace all of the braided lines, ventilation chamber, tank cap, etc.. I did one segment of line at a time, so as not to confuse myself. Now the engine won't turn over from lack of fuel.

Spark is good, compression is good. The car will turn over on starting fluid only.

I thought that their might be air in my fuel lines, so I pressurized the gas tank and forced fuel through the system while I had someone at the engine hook the fuel lines back up.

I'm thinking that my fuel pump could be bad? Can I bench test it?

Sat Nov 07, 2009 9:50 am

devnull34 wrote: ....I'm thinking that my fuel pump could be bad? Can I bench test it?

Electrical or Mechanical fuel pump?
- If electrical, then connect it up to the battery on the bench.
- If mechanical, then push the lever on the bottom as the rod in the engine case does.

You did not say whether the fuel was making it back to the engine. Pull the fuel line from the tank at the pump and see if it flows out of it by gravity. If not, then your line is plugged somewhere.

if you system is fuel injected, then I'll step aside as I have no experience with F.I. VW's.

Sat Nov 07, 2009 9:53 am

The pump is electrical, and the fuel is making it to the engine when cranking. The system is fuel injected.

Sat Nov 07, 2009 12:30 pm

This may sound stupid, but it happens... did you reverse the hoses accidentally?

Sat Nov 07, 2009 12:46 pm

I don't believe so... When facing the engine with cylinders 3 and 4 on my left, the fuel supply line comes in. The return is on my right where cylinders 1 and 2 are.

Sat Nov 07, 2009 1:50 pm

The fuel pump doesn't seem to be turning off at all. Even with the keys out of the ignition the pump is still pumping away. Is it on some sort of relay that keeps it going until the fuel pressure is just right?
The fuel flow is good - goes into the engine bay and back through the return line. Doesn't seem to be any blockage. Why won't the fuel pump shut off?

Just to be clear, the return line should be on the 1 and 2 cylinder side, right?

Sat Nov 07, 2009 3:09 pm

Find the double relay ( I think that on a beetle it is under the bck seat) and give it a sharp "rap" with a screwdriver handle. It has points in there that may be stuck for some reason.

After you confirm that the wires from the battery to the starter and the chasis ground strap are all nice adn clean and tight, I want you to run a new 12 gauge ground wire to the screws that hold the DR in there. If that doesn't make the fuel pump shut off, I want you to take the top off the AFM unit and make sure that nothing is keeping the silver prong from grounding out against the little copper strip. It sort of looks like this when the fuel pump is grounded out....

Here is a good rap on troubleshooting the DR

http://itinerant-air-cooled.com/viewtopic.php?t=54...highlight=

Tue Nov 10, 2009 5:03 pm

Thank you very much for the help with the top of the AFM unit. I had the cover off of it for about two seconds before I saw that the strip was not making a connection. Flipping the AFM over, I saw a bunch of gunk behind the flap preventing it from closing and a ground being made. So the mystery of the ever flowing fuel pump is solved! Thank you.

Now I just need to get a solenoid on my starter and get the timing all sorted out. Tried starting it from a push but I don't think we got it rolling fast enough...

Thu Nov 19, 2009 6:29 pm

Hrmm... Just got back to working on the beetle again after getting a new starter solenoid installed. Engine cranks but doesn't turn over.

I have spark at every plug. Timing is good...never changed it but checked it anyways.

Fuel pump is working the way it is supposed to now. My double relay and AFM are both good. Fuel pressure good.

Engine WILL start for a few seconds off starting fluid and sounds good when it does. No backfiring, shaking, etc..

So, I am thinking it is still a fuel problem. Ideas?

Thu Nov 19, 2009 8:05 pm

In short this is how it works....

When the engine is being started, the fuel pump runs off 1/2 of the double relay from the starter.

Once the engine starts for a couple of seconds, the little flap or door inside the AFM works a microswitch and runs the fuel pump off the other 1/2 of the double relay. Start by making sure the little door in there is free to swing and is actually running the fuel pump. Use a long thin screwdriver.

If that doesn't work, you need to trouble shoot the DR adn make sure it is well grounded via the screw that holds it in place (even if you have to run a new ground wire to the DR).

http://itinerant-air-cooled.com/viewtopic.php?t=54...highlight=

http://www.type2.com/bartnik/dblrly.htm

By the way, got this?

http://manuals.type4.org/ljet/

Also, the thermotime switch is what tells the ECU that the engine is cold and will allow the cold start valve about 8 seconds to squirt fuel in there to give the engine an extra shot of richness to get it going. Are you sure the injectors are firing? Have someone try to start the car while you feel the injectors with yoru finger to feel if they are clicking. Clicking = firing fuel in there.

Thu Nov 19, 2009 8:12 pm

I'm on the third injector right now... I've been pulling them out and watching them squirt, continuity, etc.. I don't think the injectors are the problem, but I like where you are going with the DR. I'll let you know what I find.

Sat Nov 21, 2009 12:23 pm

Couldn't find where to test the series resistors - I don't know where they are physically located. However, the double relay seems to be dead in parts. 88b should have system voltage and has nothing. There is also an audible rattle when I shake the double relay (like a contact has broken). The lack of system voltage on 88b makes sense, since my fuel injectors are not clicking when in the engine.

So, I'm thinking to replace to the double relay unless anyone else has suggestions. :)

Sat Nov 21, 2009 2:00 pm

A double relay from a bus will work for you (if that helps any).

Rare for a series resister to go bad. Look a the connections first.

Sat Nov 21, 2009 3:03 pm

Ordered a new DR... will let you know if thats the problem. Thanks. :)

Sun Nov 22, 2009 12:17 pm

While you are waiting for the DR to show up, you may want to remove the ECU and make sure that the "big plug" is fitting well into the ECU. Sometimes one of the little pins gets pushed in so that it is not making contact.

I would use some electrical contact cleaner and my volt ohm (on impedence and continuity) on the engine wiring harness to verify everything is making good electrical contacts. It is free to do and at least you will be able to rule that out.

Fri Nov 27, 2009 2:16 pm

Got the new double relay in today with the same results as before: only runs on starting fluid.

I got great continuity through my harness - I probably tested more wires than needed, but that much is ruled out.

I'm curious though, in an earlier post Randy said "make sure it is well grounded via the screw that holds it in place" about the double relay. The base of the relay is made of plastic - and the only ground I can see would be on terminal 85 of the DR. I'm going to check to see if I have a good ground again.

Is there a way to distinguish what wires go to what injector? Does it matter? I was switching them around and crossing my fingers, hehe.

Fri Nov 27, 2009 5:28 pm

So after smoking a cigarette or two, I realize that my FI beetle needs more than 3 to 5 psi in the fuel line. It isn't carbureted. *mutter* I'm supposed to be looking for something more around 25 psi. Right?

My questions have kind of shifted focus now - since I have tested the FI electrical system all the way. Is the pressure regulator on the back of the engine tin? Would it be possible for the injectors to not even squirt with such a low fuel pressure?

Sat Nov 28, 2009 1:17 pm

Nevermind, problem remains even with great fuel pressure. Injectors not clicking while cranking.

Sat Nov 28, 2009 6:05 pm

More troubleshooting this evening...

Follow along with the diagram at http://manuals.type4.org/ljet/introduction/ljet21.htm if you haven't memorized it, hehe.

Terminal 10 on the ECU to 88b on the double relay had no continuity. Ripped apart my wiring harness and replaced the wire. They have continuity now and terminal 10 to ground checks out now.

Checked continuity from ECU terminals to injection valves - they all checked out with only a few ohms resistance (2-3). Oddly they would go to the wrong side of the engine. For example, ECU terminal 14 corresponds to cylinder injector valve #4 while the harness is leading to the #1 and #2 side of the engine. Could the legend be incorrect in the link above?

Injectors definitely worked off a 9v battery. Going to test for voltage tomorrow - can anyone think of anything else to do?

Anyways, car still won't start - but Taco Bell had just arrived via the wife so I am done for the day. :P

Sun Nov 29, 2009 12:07 pm

Okay, so each of the injectors get voltage when the ignition is on. I crank the engine and they all still have voltage. Doesn't that mean the ECU isn't grounding them out to allow them to spray? I realize its very fast voltage change and the meter might not be able to see it. It also drops from system voltage (around 12v with ignition on) to around 9v with the engine cranking.

Bad ECU?