Need some help: FI hard start, dies on idle

[furgo]

This is a bit of a frustrating story. The bus was running fine, but one thing I thought I should definitely do before going on holiday was to replace the fuel lines. And so I did. After having completed the job successfully (or so I thought) we were about to start the holiday drive today, but the bus won't really start.

In summary, if you want to skip the long read ahead (I was purposely verbose to preempt questions and make diagnosing easier):

- It takes quite a lot of cranking to start
- Without depressing the gas pedal, the engine won't start
- At the times it then does start, the gas pedal must still be depressed for a while to prevent the engine from dying. At some point the idle will then be self-sustained, but the engine might die after a while as revs start going down. It does not give me too much confidence to do long drives in this situation.

Here's what happened:

1. Installed pressure gauge on the test port of the fuel ring
2. Refilled the tank with about 20 liters of fuel (ca. 5.3 gallons). I had drained it before doing the fuel line replacement
3. Before the first start, with the ignition on, I pushed the AFM flap to get the pump running. The idea was to build initial pressure and to measure it.
4. Pressure was 2.7 bar solid (39 psi) while the pump was running (and engine NOT running). I could also at least once hear the fuel returning to the tank via the fuel pressure regulator. So far so good.
5. Once I stopped actuating the AFM flap and the fuel pump was turned off, pressure dropped to about 2 bar (29 psi)
6. About 5 minutes later, pressure had dropped to 1.8 bar (26 psi). I believe this is normal.
7. Started the bus. It didn't take much cranking, but as usual, I had to press the gas pedal to let more air in. Success!
8. Started to reverse (I was parked in a tight spot) and carefully maneuver.
9. After 1-2 minutes, the engine stalled. It might actually been me while maneuvering, but I seem to remember revs going down.
10. Tried to start again, lots of cranking, no joy. Tried again, the same.
11. Had to push back the bus to the garage.
12. Double-checked vacuum hoses for usual suspects. All connected and seemingly tight
13. Double-checked FI harness connectors. All good.
14. Checked oil level. Near the low mark. Refilled until top mark.
15. Tried to start again. Very hard start: extended cranking while depressing the gas pedal. Several times it would seem to start, but it would die as soon as I took the foot off the pedal.
16. Tried once more. Same as before (hard, long start), but this time I kept the foot on the pedal and wouldn't let it die. Managed to start it, but not a good feeling. If I can trust the tacho, revs were slightly under 800 rpm.
17. Left the engine running, measured fuel pressure: 2.3 bar (33.3 psi). Within spec.

At this point I left it and I thought I'd start going through the possible causes. I didn't feel confident to drive a few thousand miles in this situation.

Here's what I had done:

In case it's relevant. I did a few things more than just replacing the fuel lines while I was in there. Some examples:

Detail of replaced fuel ring (please ignore the disconnected vacuum hose and missing harness at the time of taking the picture)

Detail of restored FPR and new vacuum control line connectors

And the full list:
- Replaced all fuel lines with 7.3 mm Cohline 2240 FI hose
- Replaced all hose clamps with 13 mm stainless ABA clamps
- Removed rust from metal fuel lines, then zinc-coated them
- Removed rust from injectors, zinc coated blank metal (I'll repaint them at another time)
- Replaced fuel filter
- Cleaned up fuel pump externally
- Removed rust from fuel pressure regulator, then zinc-coated it
- Cleaned up AAR
- Inspected and cleaned up molded vacuum hoses. They were all fine except the one from crankcase breather to S-Boot. I repaired a crack with Permatex Ultra Black there.
- Inspected and cleaned up S-Boot. Still elastic, no cracks.
- Replaced rusted metal connector from S-Boot vacuum hose to oil breather with the newer nylon-made part.
- Replaced all vacuum control line connectors (the small braided hose bits). The originals had cracks all over the place.
- Cleaned up oil breather. Made the small pinhole on the pressure valve free and checked it held vacuum.
- Replaced oil breather gasket. Secured it to the oil breather with Hylomar M.
- Removed rust and cleaned up FI grounds

Here's what I measured:

- Fuel pressure, values within spec and as stated above
- Auxiliary Air Regulator: while it was on the bench:
• At ambient temp, the gate valve was half open
• After a few minutes in the freezer, the gate valve was fully open
• Back to ambient temperature, the gate valve was back to half open after a few minutes
• After applying 12 V between its terminals, the gate fully closed after 2-3 minutes
- FI grounds measured at pins 16 and 17 from the ECU connector, harness side: 0 Ohm to ground star connector on the engine.
- TSII (engine temp sensor). Within spec at ambient temperature, resistance decreased as I wrapped my fingers around it and increased temperature.
- Oil level just below max mark (15W40 Castrol GTX), changed a couple of months ago.
- Battery full (12.76 V)
- On the bench, the fuel pressure regulator holds vacuum (tested it with a hand vacuum pump). However, when installed on the bus, it puzzled me that it also holds vacuum, but there was no pressure drop on the line. I would have expected for it to return fuel to the tank with applied vacuum. Perhaps it needed to be applied a higher vacuum? I went up to 15 inHg (half the scale of my pump)
- In terms of holding vacuum, I tested the following:

• EEC valve: OK
• Vacuum advance can: OK
• Fuel pressure regulator: OK (with the caveat mentioned abovet: vacuum held, but does not seem to have an effect on pressure - I would have expected it to drop)
• Oil breather pressure control valve: OK

Here's what I think:

- Fuel lines and pump are ok: no leaks on sight, solid pressure on the higher range of the spec. No high pressure to indicate a pinch or knick. It's the major change I made though, so there might be something in there.
- Vacuum leak? Not sure where to start looking, as I already replaced the vacuum control lines. S-Boot and molded hoses looked ok.
- I did not test the Thermo-Time Switch or the cold start valve. I know I might have to do it eventually, but I didn't think they would affect the idle.

Notes:

- It took me quite a while to get all the parts and find the time to do the fuel line replacement. As such, the bus had been standing for a couple of months in the garage.
- There are some constraints as to what I can do where the bus is parked right now. Although it's well ventilated garage (main gate is just a mesh that lets the air in), it is essentially a shared car park. So unfortunately I can't leave the engine on to do things such as timing adjustment. I'd have to get the bus towed to do this outside.

I'll try to go through the AFC manual checks now, but I'm a bit puzzled, as the separate components seem to work. Any help to go on the road and start holiday will be really appreciated! Otherwise it'll be plan B with the car: not too dramatic, but definitely not as fun as the bus

Thanks!
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[KentABQ]

Well done! That's the best, well documented posting I've read on The Samba.

I only wish I had the knowledge and xperience to help you, but I'm sure you'll be getting inundated with help soon. In the meantime, I'm eager to hear what the solution will be. It's suspenseful, waiting to hear the result.

[busdaddy]

Great post indeed!
After all that vacuum line fixing and crack repair you may have to lean the idle mixture and open the idle speed screw on the TB up to undo previous adjustments that were done to compensate for the leaks.

Try unplugging and grounding the TS2 wire first, then try disconnecting a small vacuum line and leaving it open, the TS2 will lean it and the open line will add air, see if it's worse or better.
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[raygreenwood]

[furgo]

[mainstreetprod]

Don't make the same mistake I made once, assuming that because you have fuel pressure that you also have volume. As an example, you could hook your fuel pressure gauge to an air compressor and it could show 50psi without fuel. Get a medium fast food drink cup and hold it under the open fuel line while you actuate the AFM. If it can't fill the cup in a few seconds, you have a volume problem. A restricted filter or kinked line would do this, but might still show adequate pressure.

[SGKent]

it is not uncommon to forget the wire harness plug behind the AFM

Make sure if any wires were removed they are back on the same spot. This includes the ECU wire at the coil

put a teaspoon or squirt of gas in the S-boot and see if that makes it better or worse. That will tell you if you are running too lean or too rich.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Wildthings]

It is possible that one of your old hoses had been intentionally plugged by sticking something down inside it. This would have been done because the dashpot on the air cleaner, the vacuum advance unit, decel valve or other was not holding vacuum. By replacing the hose you thus now have a vacuum leak.

Maybe try to blow through all your old hoses and see if any were plugged or remove each of your new hoses one at a time and plug their ports to see where a vacuum leak might be.

[furgo]

[busdaddy]

[furgo]

Thanks everyone for the help. Let me address the suggestions one at a time:

[SGKent]

open the hatch and look down at the AFM. Is the plug in the back? That is easy to miss because it hides behind things except when looking down from the top.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[SGKent]

there are also two set of vacuum lines.

One set is the distributor and EEC valve on the air cleaner. That goes to ported vacuum. Meaning no vacuum unless throttle is open.

The other set is the decel valve and the fuel pressure regulator. That goes to the manifold (plenum) vacuum. It has vacuum all the time when the engine is running.

Make sure those are not mixed up.

Also your photo shows no wires to the injectors or CSV. Was that harness completely removed?
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[aerosurfer]

No one has said anything about ignition? Are your wires connected properly and what's the status of your points?

I agree with what Steve said about checking the connections at your ECU and AFM to see if any pins got pushed back into the harness. Even using a multimeter to test continuity on all harness connections. Double checking all connections points on the harness is free and easy to do. I had a pin in my double relay push out of the plug and it made for very hard starting. Unfortunately not the other other symptoms you are having though

Fuel pressure is great, but do indeed make sure you are getting outflow from the injectors. Check the wires and connection to the series resistor.

PM me about your shopping list.... I get a very healthy fedex discount through work and it may be cost effective to ship it to me and I can send it on.
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[furgo]

[furgo]

[SGKent]

2 cents worth. Might back up at this point and look at each of the 3 items needed whether they have been done before or not.

1) Is there spark consistently? Put an inductive timing light on it and see. Point blocks break sometimes, condensers go bad. Wires get accidentally put on the wrong spot.

2) If a teaspoon of fuel is added to the S-boot does it fire better or worse. That will tell you if it is getting adequate fuel or too much.

3) Put a compression gauge on it. Were the valves adjusted? Do they warm up and expand to where they are open thus killing the engine at idle. A compression test when warm will answer this.

If you have all three it should run. Once you determine where the weak link is you can focus on that area. Your lists are extensive which is good, but if you can narrow it to one of the 3 you will find it easier from here out.

It can also be a mouse built a nest in the exhaust and once it starts back pressure kills it. Those things happen too.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[furgo]

Thanks, I appreciate the help. Some comments and questions. Apologies if the questions are basic, my background is not mechanical and I'm effectively learning from scratch here.

[vwwestyman]

[furgo]