TheSamba.com :: View topic - Air flow meter (AFM) plug

Sat Nov 14, 2009 8:02 pm

I have a 78 fuel injected 2.0 Westy.

On the back of my air flow meter (where the plug goes in) there are seven terminals sticking out and the plug that goes into it has seven slots but only 6 of those have metal connections. Is this normal?

My fuel pump will not run (and hence the bus will not run) and I'm trying to trace the source of the problem. The fuel pump, filter and lines are brand new. It has power when you crank the engine but nothing makes noise when you have the ignition on and move the AFM arm. I traced the wire leading from the fuel pump to the double relay (fuel relay) and the connections are intact. What else would cause the fuel pump to not work??

Sat Nov 14, 2009 8:29 pm

ziggybean wrote: What else would cause the fuel pump to not work??

A bad fuel pump.

Sat Nov 14, 2009 8:48 pm

VDubTech wrote: ziggybean wrote: What else would cause the fuel pump to not work??

A bad fuel pump.

Or a bad ground at the relay.

Sat Nov 14, 2009 8:49 pm

Man, I can't have two bad fuel pumps in a row. Something else has got to be going on. What about the fuel relay? How do I test if that's bad? AFM? I turned in the ignition on and can't find any power to it. Does that only turn on when the engine is cranking too like the fuel pump?

Sat Nov 14, 2009 9:47 pm

I believe a 78 should have 7 leads into the harness. If you can pull the sleave back, see if one got pressed out of the plug. Also you can make your pump activate by moving the AFM air flap open while the ignition is ON.

Sat Nov 14, 2009 9:54 pm

So I pulled one of the fuel lines in the engine and there's fuel so the pump must be working but it doesn't make any noise. I can't make the pump activate by moving the AFM air flap open while the ignition is ON.

I pulled one of the spark plug wires, cranked the engine, and it made a weak spark once but wouldn't spark again. Any ideas?

Sat Nov 14, 2009 10:01 pm

The seventh connection was stuck in the cover - moved it back to where it should be but she still won't start.

Sat Nov 14, 2009 10:07 pm

Test to see that power reaches the pump w/ a voltmeter, then start working back to the double relay. The service manual has a routine to test the double relay. Also stated above see the DR is grounded properly.

Sat Nov 14, 2009 10:57 pm

Well, accoring to the double relay test, my double relay is bad. Everything checked out okay until I ran the starter, and tested the current between terminal 85 and 88d which means that the pump relay isn't closing. I'm guessing this would cause my van to not start? :) Hopefully...? hehe If this isn't it I'm going to scream.

Sat Nov 14, 2009 11:17 pm

Yeah, I had a double relay go bad that would cause the bus not to start. Only it was intermittent, sometimes you could wait a few moments and try again and it would fire right up.

Since the relay did test bad according to the Bentley, I replaced it. You can get a new one for about 70 bucks from Bus Depot or CIP1. They come with a plastic body now instead of the original metal ones.

After I replaced it, I popped open the defective one and saw the circuitboard was corroded badly on one corner. Water had probably gotten in after years of being mounted in the engine compartment and not hooked up (the bus was carbed for a little while).

Haven't had a problem since replacing the double relay.

Sat Nov 14, 2009 11:38 pm

Mine already has the plastic one so its probably been replaced before. The plastic between the terminals had rust residue when I initially pulled it off.

Sun Nov 15, 2009 9:56 am

So I just realized that I was doing this entire test on the plug that goes into the relay and not the terminals on the relay itself. I'm guessing I should have been doing it to the relay terminals?

Well, I just did it to the relay terminals and there is no power going to the relay on any of the terminals it says to test so there is no power coming from the + end of the battery. How do I resolve this?

Sun Nov 15, 2009 10:41 am

I got the fuel pump to hum! The arm in the AFM wasn't making contact! But the engine still won't start! :(

Sun Nov 15, 2009 11:18 am

Might be a spark or timing issue now? I've got the wires aligned on the cap to fire in the 1-4-3-2 order. I'm not sure where to start next to trouble shoot this?

Sun Nov 15, 2009 11:38 am

Just ran another test. The fuel pump works with the ignition in the ON position but only when the AFM flap makes contact. if I crank the engine, there is not enough contact in the AFM to activate the fuel pump. It bounced back and forth off of the contact so there is no hum or clicking from the fuel pump. Any ideas?

Sun Nov 15, 2009 11:41 am

Check the wires between the DR and the starter.

Sun Nov 15, 2009 11:51 am

Is there any way to mess up how the wires attach to the starter?

Sun Nov 15, 2009 11:57 am

When the key in the ON position there is no power to the wires plugged into the starter. Are these fed from the relay?

Sun Nov 15, 2009 12:11 pm

I found this in another forum: "Do you have spark at the plugs? If not(after you get the timing sorted) work backwards in the electrial to see where the spark is "lost". I like to check that spark is making it past the coil. If you have spark out of the coil, it has to be distributor problem. Sounds like you have fuel so should be good there. I think once you get the timing fixed you'll be good to go. And...go get a new battery" http://www.thesamba.com/vw/forum/viewtopic.php?t=386183&highlight=engine

We have a spark out of the coil but a very weak spark if any at the plug. Need new distributor?

I'm not sure if the fuel pump and loss of spark are a related issue?

Sun Nov 15, 2009 12:17 pm

Correct wiring at the starter.....

From Ratwell's site....

"15.2) Close-up of the starter wiring partially removed. It's hard to mix up the wires because of the ring terminals but on terminal 30 you should have (1) large red wire for the alternator, (1) large black wire for the battery, (1) red wire for the heater booster fan and (1) thick red/white stripped wire for the fuse box. The large cables are usually wrapped in a beige sheath.
The red/white wire triggers the fuel pump via the double relay. In this photo you can see that I've got a hot start relay installed and the blue arrow points to one of the relay's wires. Normally the black/red wire which is connected to the blue wire of the relay connects to terminal 50 where I have the black wire from the relay. An large red wire on terminal 30 powers the double relay. All the red wires can be confusing but again remember all the ring terminals connect to 30."