Fuel Pump vs ECU relay: Intermittent failure feels different?

[Vanagon Nut]

I appreciate that diagnostic help John.

I'll swap in a different pump. I have no desire to try backflushing the existing pump, if that would even help.

While searching here for info on the pump check valve, found this page with images showing internals of the Bosch fuel pump:

https://www.thesamba.com/vw/forum/viewtopic.php?t=706463&highlight=chinese+fuel+pump

It appears the check valve is plastic?

Before I noticed this issue, I'd poured in some injector cleaner / "upper cylinder lubricant". Its viscosity was quite thick. I now wonder if it hasn't some how fouled the pump check valve.

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[crazyvwvanman]

If the fuel pump check valve was sometimes releasing residual fuel pressure back to the tank, how would that make the engine too rich at next start up?

If you want to know if system pressure is sometimes being released why not MEASURE IT. Install a gauge where it can be left ALWAYS connected until you solve this problem. Look at the gauge every time you stop and again every time before you start. See if there is any correlation between the readings and the occurrence of the problem. Once you know that loss of residual pressure is related to your problem then you can work on pinpointing it.

Mark

[Vanagon Nut]

Thanks Mark.

The fault occurs more reliably after driving into town, shutting it off, running errands etc. I had considered leaving the pressure test gauge connected while doing that but for various reasons wasnt comfortable doing so.

IF the pump check valve released residual fuel pressure while the nose of van was raised, would more or any fuel remain in the supply hose, fuel rail etc. VS the same event with van level or front lower than rear?

I recall testing for the fault with front of van raised 4.5" while doing other work. I could not recreate the fault even after many tests (different engine rest periods)

When the hydro power comes back on ill do a volume test then try to recreate the fault with a pressure gauge connected after idling the van in my shop.

On the Windy windy Sunshine Coast,

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[82westyrabbit]

Leaking injectors are causing the rich mixture or flooding at start up. The fuel pump if a problem at all is not catching up so once you have cleared the flooding you now have no fuel the start the engine. So I believe there is two separate problems going on here. I have only had symptoms like this in cars that had severe fuel contamination problem that show up after the initial problem was fixed. But of cores I am a armchair quarterback from 3500 miles so I could be out in left field somewhere. If it was easy Niel would have it fixed already. John

[Vanagon Nut]

I did some tests.

No fuel leaks or kinked "hard lines", fuel filter is new.

Fuel delivery: in excess of 500 cm3 spec. i.e. at 30 seconds, container was filled to ~ 800 ml.

Engine cold, fuel pump relay bypassed pump turned on then off: fuel pressure was 39 PSI. In 10 minutes pressure dropped to 35 PSI. Doing same then clamping supply hose; no drop in pressure. Opening clamp, pressure dropped. I could not re create these pressure drops and did not see any residual pressure loss when no starts began to happen.

Engine cover on, engine on - off for various periods of time;

engine running, fuel pressure was 34 PSI. Engine shut off fuel pressure rose to 38-40 PSI. No starts began when engine was off for more than 20 minutes. Two no starts in a row, fuel pressure bled off at gauge, the engine started. The third attempt of same did not work. I had to hold the throttle wide open.

On one no start disconnecting the idle stabilization valve allowed the engine to start likely because unmetered air was allowed into the intake. The valve checked out ok. (resistance, amp draw at idle) and swapping in a spare valve made no difference to no starts.

I think the pump check valve is ok. It's almost like the system is over pressurizing or vapour locking after the engine is shut off. Regulator at fault?

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[djkeev]

Did you pull the injectors, place them in a container and see if they leak with the hot engine off?
This is really easy to do.

Dave
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[Vanagon Nut]

[82westyrabbit]

Hi Niel. I think you need stop trying to figure it out until you have the new injectors in that’s probably most of your problems. Drive it if you can risk having to play with it to get it to start. That might help in itself. Just pick off one problem at a time until you get it figured out. John

[Vanagon Nut]

Thanks John. Good advice.

The van does drive, always starts cold, and starts 90% of the time normally. And, I'm fairly certain there's no related safety issue (e.g. fuel pressure too high at times)

I won't plague this thread further but I've narrowed down hot engine no start causes to three things:

- leaking injector(s)
- fuel regulator
- idle control valve not opening far enough or remaining closed

I'll also ring out the ECU connector to double check my wiring work.

I still hope to take this van on a long trip soon. Narrowing down the no start causes does provide some peace of mind.

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[Vanagon Nut]

Hi all.

Just to report back.

Engine cold, started fine, I briefly ran engine then removed the old fuel injectors. Each injector tip was wet with fuel. That may be normal? But, nearly all injector tips had bits of black debris, #2 had the most. Maybe intake plenums are dirty? (did not clean at time of engine rebuild. ) Black dirt above O ring likely due to an external engine oil leak. Spark plugs somewhat black coloured. Rich fuel mix?

Aftere installing 4 pro cleaned, tested, serviced fuel injectors, hot start issue remained.

Air cleaner filter was good clean used at time of swap but I may replace it. I'll check again for vacuum leaks but will use starter fluid or propane to do so. Though fuel pressure tests seemed ok, I'll swap out the fuel pressure regulator again. Vacuum hose to regulator may have been too small an ID. (white plastic vacuum hose off a Digifant engine) I replaced that.

Hot start issue prior, and now is consistently temporarily resolved by:

- disconnecting the idle control valve electrical connector
- disconnecting the EVAP purge valve vacuum hose at throttle body. (this allows more air into intake)

It seems that allowing a little more air (or any) into intake allows engine to start when hot start issue occurs.

I'll swap in a known good ISV again but IIRC, doing so made no difference. Of note, engine hot, idle can dip, surge, when disengaging clutch at lower RPM while coming to a stop. Classic idle control symptom.

Theories:

- with engine mounted at 50º, exhaust manifold/engine heat gets soaked by ISV, causing valve to stick too far closed. There is no heat shield at exhaust manifold.
- ECU is at fault
- I've incorrectly wired the ISV. But, the engine runs, idles totally fine 90% of the time, ISV wiring rings out ok.
- "rich" mix due to fuel pressure regulator

The ISV on this engine controls all air idle unlike the WBX Digifant which has a bypass screw on throttle body. I read online of installing a heater valve in lieu of the ABA ISV. For testing purposes, this kind of makes sense.

Neil.

images of old removed injectors yet to be serviced at ~ 7500 miles.

#2, 3

#2

#1

no oil on injectors at ~ few hundred miles

_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[Vanagon Nut]