79 Bus Fuel Injection Resurrection

[AzironaZack]

Hey all,
In the past few days I finished up the conversion BACK to fuel injection on my bus. The bus is a '79 California model with the CA exhaust. The fuel injection system was lifted complete from a friend of mine's '78 Federal bus.

The donor bus had been running well enough for a couple of years when it suddenly lost compression in one cylinder due to ring failure. My friend really needed to drive it one day and was pushing it hard on 3 cylinders when he heard a big ker-chunk followed by another and another and another, etc. He didn't have the time nor energy nor money to do a rebuild or replace the engine so he sold the bus cheap. Before he sold it, I bought the fuel injection system from him.

That's the back story.

I pulled the engine and transmission from my bus and gave them both a serious cleaning. Everything removable from the engine was removed, cleaned, and reinstalled. I installed the FI stuff on the engine and reinstalled it along with the trans.

Just a couple days ago I finished repairing my wiring harness (I had two, you see, one with good supple wire and many broken connector bodies and one with very crispy wire and many sound connector bodies). I was very careful to make sure to not make any mistakes with switching around terminals or anything.

I got all the electronics installed and slapped on the air cleaner and AFM and S-boot and hooked everything up all nice and neat.

While my daughter cranked the engine I fiddled with the distributor (onto which I'd installed a new cap and rotor the day before) until I got to the sweet spot where the thing would run. She was thrilled when the bus first turned on, as was I. The bus ran for about 5 or 6 minutes, then died. It turned out that the cheapo fuel pump from the donor bus had met it's maker (it had gas in it that was allowed to dry up for 8 months or so). The pump would output plenty of volume and pressure for about 3 seconds, then it would start making a screaming sound and volume/pressure fell to practically nil.

I picked up a new Bosch pump today and installed it, whistling zippity-doo-da the whole time thinking about how nice it's going to be to drive the bus home tonight, etc. You know the feeling.

But (it seems there's always a but) the bus wouldn't run when I cranked it. If I squirted some starting fluid into the s-boot it would start and run on that, but it wouldn't keep itself running. I was depressed, despondent even, but not for long.

I checked to make sure that the pump was working by manually operating the AFM gate. The pump was working. I heard all the bubbles that had gotten into the fuel rail gurgling into the fuel tank and thought, "Oh, that was it, just some air in the lines." When I went to start the bus though, it ran for just a moment then quit.

I decided to try disconnecting the AFM. Wouldn't you know it, the engine started and ran with the AFM disconnected.

I decided to try some simple stuff. Since the valve rockers had been removed (and when I installed them I neglected to adjust them since the lifters had certainly bled down by then) I went ahead and adjusted the valves (1.5 turns past contact).

I slapped a timing light on the thing and timed it to 7.5 BTDC at 780 RPM (which is about where it floats when the AFM is disconnected).

I checked dwell: 58.4 degrees. I know that this is just barely outside of the envelope for tolerance but I didn't want to fark about with replacing the points in the dark.

Tomorrow I'm going to get down to some more troubleshooting. I'm thinking of the usual suspects: vacuum leak, worn fuel pump switch in the AFM, points too far out of spec.

If anyone wants to offer some words of wisdom, please feel free. I figure I'll work my way through the L-Jet troubleshooting guide.

What's boggling me is how the thing runs with the AFM disconnected. I was even able to drive it home like that (although it wasn't much fun). What does it mean when my bus runs with the AFM disconnected but doesn't when the AFM is hooked up?

Thanks for reading the ramble, and thanks in advance for any tips.

[justgimmecoffee]

you might check your fuel filter, depending on age.

Let us know how it goes.

[Amskeptic]

What's boggling me is how the thing runs with the AFM disconnected. What does it mean when my bus runs with the AFM disconnected but doesn't when the AFM is hooked up?

I think it means that it might be running rich as a pig, and no AFM is helping it not to drown. But wait! There's more. The engine should stall right out with the AFM disconnected, because the safety circuit to the pump relay depends on the 36/39 contacts being closed by the movement of the vane.

So, we need to check a few things. When the engine is sitting there idling with no AFM connection, is the fuel pump running?

If you hook up the connector, is there a change in fuel pump behavior, like if it was running does it stop when connector is plugged in? or if the fuel pump was not running before, does it start running when you plug in the connector?

If the pump has been running through this whole bizarre situation, then let's try another test. Get it to idle with the connector off, and when you plug the connector in, grab the little wiper in the AFM, and see if you can find a new spot that allows the engine to run with the connector in (if plugging in the connector shuts the engine down instantly, no nothing nada, you have an electrical issue) If my hunch is correct, moving the wiper about 1/4 to 1/2" clockwise the second you plug in the connector at idle, will allow the engine to keep running. Try to find the happy spot, and get back to us.
Colin

[AzironaZack]

When the engine is sitting there idling with no AFM connection, is the fuel pump running?

No, it's not running. This is seriously surprising. I didn't know that a fuel injected engine could run without the fuel pump pumping. The fuel pump does run while the starter is cranking but once the starter stops cranking the fuel pump turns off.

If you hook up the connector, is there a change in fuel pump behavior, like if it was running does it stop when connector is plugged in? or if the fuel pump was not running before, does it start running when you plug in the connector?

When I plug in the connector the fuel pump starts running.

(if plugging in the connector shuts the engine down instantly, no nothing nada, you have an electrical issue)

Plugging in the AFM does kill the engine pretty quickly. It's not instantaneous though. What happens when I plug in the AFM is this:
0) The fuel pump comes on immediately
1) After about a quarter second the idle speed increases, but not by all that much. Probably takes the idle from 780 to 800 or 820.
2) The faster idle persists for about half a second to 1 second then the engine sputters and turns off.

If my hunch is correct, moving the wiper about 1/4 to 1/2" clockwise the second you plug in the connector at idle, will allow the engine to keep running. Try to find the happy spot, and get back to us.

I can find "happier" spots, but no such place as a happy spot. When I turn the wiper by hand clockwise (towards the closed-vane-engine-not-running, position) about 1/4" the increased idle (part 2 above) sometimes lasts as long as 2 or 3 seconds before the engine quits.

[dtrumbo]

Just slap me now for even suggesting this, but is it possible you have the '+' and '-' wires on the fuel pump reversed which would cause it to suck instead of pump? Let's just say that during cranking the cold start valve is squirting enough for the engine to start and with the AFM unplugged, enough fuel is passing through via gravity to keep the bus running. Then when you plug the AFM in and the pump starts running backwards it stops the gravity flow and the bus dies. A long shot for sure, but it's worth checking.

Patiently waiting to be slapped.

[Amskeptic]

Just slap me now for even suggesting this, but is it possible you have the '+' and '-' wires on the fuel pump reversed which would cause it to suck instead of pump? Let's just say that during cranking the cold start valve is squirting enough for the engine to start and with the AFM unplugged, enough fuel is passing through via gravity to keep the bus running. Then when you plug the AFM in and the pump starts running backwards it stops the gravity flow and the bus dies. A long shot for sure, but it's worth checking.

Patiently waiting to be slapped.

I also entertained a similar notion. I think it might be a buggered AFM . Subsitution with a known good unit might be a good idea.
Colin

[AzironaZack]

Well, it turns out that it was simple. Thanks to dtrumbo for reminding me that the simple things are critical.

The fuel pump was installed correctly and was pumping in the right direction. The problem was that it wasn't pumping enough gas! When doing a flow test it would pump full bore for about a second then the flow would drop to a trickle and the pump would start making noise.

It turns out that I had a clogged fuel filter. When the bus sat for a few minutes between starts, the fuel filter would have time to fill with gas and fill the fuel pump's inlet too. This was the gas that pumped properly. Once that gas was used up, the trickle started.

I've read about others making the mistake in the past but I've never done it myself until now. The mistake I made is that I used an old steel gas can that had been sitting around empty for about a year after it's last use. I used that can to fill up the bus and I think I introduced a bunch of rusty/dusty bits into my gas tank.

So… putting a new fuel filter on solved the problem and the bus now runs as expected, with the AFM plugged in. I'm going to pick up a few more fuel filters today just to have them on hand since I anticipate clogging a few more before I've cleared the tank of all the crud. If anyone has any tips on how to clear the tank without removing it, I'm all ears.

Thanks for the help everyone. Fuel Injection Rocks! For the first time in my 3 years of owning it it's actually driving like it should. Good power, good throttle response, smooth acceleration. The single weber carb I had on there before never did half as well as this. I can accelerate up an onramp doing 40 mph in 4th gear! That would have bogged won the old system for sure.

Ahh, sweet success.

[dtrumbo]

Fuel Injection Rocks!

Yes it does! I'm glad you're up and running. As far as your fuel, I think I'd drain the tank into known good, clean containers and then pour it back through some type of filter (cheesecloth?). That might get the big chunks out and then having the extra filters handy will get you where you need to be. Congrats again!

[Bleyseng]

Well, it turns out that it was simple. Thanks to dtrumbo for reminding me that the simple things are critical.

Thanks for the help everyone. Fuel Injection Rocks! For the first time in my 3 years of owning it it's actually driving like it should. Good power, good throttle response, smooth acceleration. The single weber carb I had on there before never did half as well as this. I can accelerate up an onramp doing 40 mph in 4th gear! That would have bogged won the old system for sure.

Ahh, sweet success.

K.I.S.S. (keep it simple stupid) always works for me, look for the simple crap when fixing first.
Another single carb convert!!! Haha, I keep tellin folks the world of difference between the two....VW actually did make improvements over the years for a reason.

[AzironaZack]

Yup. When I bought the bus I told myself that the fuel injection conversion would be the first thing I did. One thing led to another and I put it off, and put it off, and put it off some more.

3 years later, it's finally finished and the bus drives like it should. I've had plenty of experience driving other FI busses belonging to my friends and so I knew the whole time what I was missing. It's a shame I took this long to do my own.

[Gypsie]

As far as your fuel, I think I'd drain the tank into known good, clean containers and then pour it back through some type of filter (cheesecloth?). That might get the big chunks out and then having the extra filters handy will get you where you need to be. Congrats again!

X2-plus: for an "extra thorough OCD job" pour the gas back in and rock the bus a bit. repeat the process until you have no more 'stuff' come out.