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Fuel Pump vs ECU relay: Intermittent failure feels different?
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djkeev
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PostPosted: Sat Dec 15, 2018 6:42 am    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Vanagon Nut wrote:


After engine was up to temp, then shut off for 10 minutes, it took 4 attempts for it to start normally. It did this twice today before any work I did to van.

----------------------------------------------------
If I held the gas pedal down, it helped it start.
-----------------------------------------------------


Oddly enough, removing the gas cap seemed to help. Fuel level was at ~ 1/4 tank.

Neil.



"If I held the gas pedal down, it helped it start."

On a fuel injected engine, pumping the gas pedal, holding the gas pedal fully down or half way does nothing except open the throttle body butterfly (and also moves the TPS switch but that is a running issue, not a starting issue if the ECU is functioning properly)

Opening the butterfly allows more air in. More air dilutes excess gas and thus the unit starts once the liquid fuel is gone and a spark can happen.

This is why I stand with the opinion that you are flooded.

Dave
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PostPosted: Sat Dec 15, 2018 1:01 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

crazyvwvanman wrote:
How about vapor building up in the fuel rail?
....
Is the fuel rail somehow oriented such that it no longer easily clears vapor out? If so, it is possibly made worse when the van is pointed uphill?

Perhaps some clear tubing on the return nipple would let you check for bubbles after letting a hot engine sit for a while, engine lid on.

Mark


Thanks Mark. The clear hose is a neat idea. Hadn't thought of engine heat causing vapour in rail.

The engine bay fuel hose routing and location on my 15º ABA Vanagon might pose a higher risk of heat soak into the fuel. (one reason I "flipped" the rail on my 50º ABA). However. That I can recall, only once did heat in fuel (In part) cause a no start on that engine.

The rear of the 50º ABA van in question was raised when hard or no starts happened.

The Mk3 Jetta/Golf ABA has a "protective plate" installed below the regulator. It might be there only to limit fuel leak spray or protect against a broken belt but maybe it also acts as a heat shield?

I may "flip" the fuel rail 180º back to its' OE position. As is, the regulator and hose connections to rail are close to ignition wires and other wiring. Since this replacement rail has no pressure test port, although a low risk, doing a fuel pressure test might allow fuel onto ignition wires etc.

internet image of ABA "protective plate".

Image may have been reduced in size. Click image to view fullscreen.


online ETKA refers to part as a "protective plate" PN 037 133 941

eBay image

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PostPosted: Sat Dec 15, 2018 1:41 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

djkeev wrote:
Vanagon Nut wrote:


After engine was up to temp, then shut off for 10 minutes, it took 4 attempts for it to start normally. It did this twice today before any work I did to van.

----------------------------------------------------
If I held the gas pedal down, it helped it start.
-----------------------------------------------------


Oddly enough, removing the gas cap seemed to help. Fuel level was at ~ 1/4 tank.

Neil.



"If I held the gas pedal down, it helped it start."

On a fuel injected engine, pumping the gas pedal, holding the gas pedal fully down or half way does nothing except open the throttle body butterfly (and also moves the TPS switch but that is a running issue, not a starting issue if the ECU is functioning properly)

Opening the butterfly allows more air in. More air dilutes excess gas and thus the unit starts once the liquid fuel is gone and a spark can happen.

This is why I stand with the opinion that you are flooded.

Dave


Hi Dave.

Yes. I agree. This is likely the fault and as per your quote, those were my thoughts at that time; pedal down introduced more air etc.

I'll re read it again but so far, in my A3 Bentley, I don't see an injector spray test procedure akin to the WBX injector test. In other words, rhetorically speaking, will the injector retaining clips hold the injectors in place while fuel system is up to pressure. At minimum, I'll re create the hot start problem then see if one or more of the plugs is wet.

I've read of some folks using methyl alcohol in place of gasoline to bench test an injector. Do you know if methyl alcohol is harmful to injector internal parts? Or use methyl hydrate?

I was thinking of using my brake pressure bleeder to pressurize each injector then watch for any leaks at injector. I can measure pressure inside the bleeder.


Neil.
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PostPosted: Sat Dec 15, 2018 2:06 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Vanagon Nut wrote:

I may "flip" the fuel rail 180º back to its' OE position. As is, the regulator and hose connections to rail are close to ignition wires and other wiring. .....



But then the Tiico has the regulator at that end so..... Think < shrugs >

Neil.
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PostPosted: Sat Dec 15, 2018 3:54 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

To see if a fuel injected engine won't start because it is badly flooded, try quickly unplugging the injector wiring plugs when the problem happens. Leave them unplugged and then try to start again and see what it does. If it briefly starts or tries to more than before that will confirm the presence of extra fuel. This should clear out the fuel and let it start again when plugged back together.

On one of my group trips to Baja a member of our party had a similar problem the first day in Mexico. When we would stop for 5 or 10 minutes his engine would then just crank away but not start. He said it had happened a few times before and eventually with a long enough wait it would go again. I suggested the above trick. It fired right up for a second. Then he plugged things back and it ran ok again. That gave him the confidence to continue the trip south, knowing there was a way to quickly get going again if pressed for time. This was a Subaru conversion.

Mark
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PostPosted: Sat Dec 15, 2018 5:15 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Yes my Tiico engine has the regulator at the rear of the engine or front of the van. I don’t think which way the fuel rail is mounted makes much difference. If you are having a problem with fuel boiling in the fuel rail it is because something is leaking and the pressure is too low. Bosch cis fuel injectors would leak and cause this problem all the time. How do the plugs look? Are we sure this is a fuel problem? Just asking.

Can you pull the injectors and just energize the pump to look for leaks? If the engine runs ok you probably don’t need to ck for injector flow rates.

I was also thinking that maybe a bad fuel pump giving intermittent low fuel pressure or a bad internal ck valve might be the problem.

Do you have any spare parts around so you can just try a few things - like a different fuel pump or different fuel injectors? I try to keep spare parts like that just for times like this.

John
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PostPosted: Sat Dec 15, 2018 7:13 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Mark: when the issue happens, as i try to start the engine it will "catch", maybe fire briefly but wont run. Thats a great tip. If disconnecting injectors isnt easily feasible, crank engine with ECU disconnected? Or, maybe disconnecting the RPM sensor (TDC sensor) or hall at dizzy would keep injectors from pulsing.

John. Me? Have spare parts? Yes! LOL. Wink. I intend to remove the fuel rail, leave injectors attached, pressurize the fuel system then watch for leaks at injectors. The intermittent cut out happened again a few times but it really seems like the hard start os a fuel issue. Maybe im dealing with more than one issue.

Do you think the clip that holds each injector to the fuel rail will keep the injectors from popping off rail once fuel is pressurized? I searched the internet to no avail on that.

The hot hard or no start is happening consistently if i leave the engine off for 10-15 minutes after its run to temp. Bypassing the fuel pump, cycling the pump wont help it start. This time, before leaving the engine off, i put the Bilstein jack at the gas pedal holding throttle open. After 20 minutes engine started fine.

Neil.
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PostPosted: Sat Dec 15, 2018 7:19 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

The point of unplugging just the injector wires is so the engine can still fire and run on the excess fuel, if there is any present. If it does, you then know there was too much fuel. If all you want to do is clear out any fuel without knowing for sure, crank the starter without the key turned on.

Mark
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PostPosted: Sat Dec 15, 2018 7:59 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

^^

ah ok Mark. I get it now and good suggestion for just clearing the fuel. I will try the disconnect injectors method soon. At least the issue can be recreated fairly consistently now.

For now, I'll test by leaving the throttle propped open VS closed during each time I let the engine sit for 10 - 15 minutes.

edit: injector connectors 2 and 3 are hard to get at. It might be possible to disconnect them with the intake upper plenum in place but plugging them back in likely means removing the intake upper plenum.

Neil.
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PostPosted: Sat Dec 15, 2018 8:42 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

You could also shut the van off by pulling the fuel pump relay. That would release the pressure. Then reinstall the relay and repeat your test. If it starts right up than you know you have leaking injectors. John
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PostPosted: Sat Dec 15, 2018 8:47 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Hmm... ok. So that fancy switched relay bypass tool I made should be great for that.

I think I mentioned this but it was interesting (to me anyways) that with that "fancy" relay bypass tool installed in the fuel pump relay socket, switching off power to the pump would allow the engine to run for nearly a full second then slowly die.

Neil.
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PostPosted: Sat Dec 15, 2018 8:56 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Yes that’s running the fuel out of the system. When you go to restart it turn the key to on wait for the pump to shut off then start it from there. Good luck. John
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PostPosted: Sat Dec 15, 2018 9:12 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Right. My brain still thinks in "carburetor" so it's an interesting thing to envision; the injectors still feeding fuel as the ignition still keeps sparking until the engine dies due to lack of fuel.

From what little I can understand, and what is shown in the A3 Bentley, disconnecting the RPM sensor (#1 TDC sensor) will kill the spark. And, it works in conjunction with the dizzy hall to coordinate sequential injection.

On one of the first test drives on my first swap (ABA 15º) if I'm not mis-remembering, in my hasty excitement, I did so with the dizzy hall disconnected. It ran like crap but ran none the less.

Neil.
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PostPosted: Sun Dec 16, 2018 5:33 am    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

82westyrabbit wrote:
You could also shut the van off by pulling the fuel pump relay. That would release the pressure. Then reinstall the relay and repeat your test. If it starts right up than you know you have leaking injectors. John


Now, here is someone way smarter than average!! ^^^^^^

So obvious yet required thinking outside of the box! Good post!

Dave
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PostPosted: Sun Dec 16, 2018 7:02 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

I drove the van during testing so I used the fuel pump connector in engine bay to control the fuel pump.

Engine up to temp, pump disconnected, engine off 10 minutes, it started fine.

Engine up to temp, used key to shut off engine. On 3 separate tests, engine off 5, 10 then 15 minutes, engine started fine each time. Rolling Eyes

I'm part way through a tank of fuel with Seafoam. If a small bit of dirt was fouling an injector valve causing it to stay open and leak, maybe the Seafood cleared it?

Neil.
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PostPosted: Sun Dec 16, 2018 8:25 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Hi Neil. Assuming you bought the engine out of the car as opposed to harvesting it from a running car my guess is the car was run on cruise control a lot and it’s final straw was fuel contamination before it went to the scrap yard. It looks like you inherited those issues based on the problems you are having. I think in business they call this a MPV (multiple problem vehicle). On my van I replaced the injectors before I even started it just because and it was cheap. On the other hand I pulled my fuel pump out of my parts van that had not run in twenty five years (I was shocked it worked at all) but I had just spent a bunch of money on the van and was not willing to open my wallet again. I have put 2000 miles on that pump and it is quite. I am sure you will get to the bottom of this. John
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PostPosted: Sun Dec 16, 2018 8:38 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Vanagon Nut wrote:

I'll re read it again but so far, in my A3 Bentley, I don't see an injector spray test procedure akin to the WBX injector test. In other words, rhetorically speaking, will the injector retaining clips hold the injectors in place while fuel system is up to pressure.


For the AEB 1.8T but fuel rail looks similar and injector retaining clips look the same.




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PostPosted: Tue Dec 18, 2018 8:17 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

82westyrabbit wrote:
Hi Neil. Assuming you bought the engine out of the car as opposed to harvesting it from a running car my guess is the car was run on cruise control a lot and it’s final straw was fuel contamination before it went to the scrap yard. It looks like you inherited those issues based on the problems you are having. I think in business they call this a MPV (multiple problem vehicle). On my van I replaced the injectors before I even started it just because and it was cheap. On the other hand I pulled my fuel pump out of my parts van that had not run in twenty five years (I was shocked it worked at all) but I had just spent a bunch of money on the van and was not willing to open my wallet again. I have put 2000 miles on that pump and it is quite. I am sure you will get to the bottom of this. John




Next time I do an engine rebuild I will send out the injectors for cleaning etc.

I finally found my 4th spare injector so I may send those out to be rebuilt then install them at a later date.

The engine was actually free but was well used. Wink Person that gave it to me claimed it was a runner and that it had about 280,000 kilometres on it.



Vanagon Nut wrote:


I'm part way through a tank of fuel with Seafoam. If a small bit of dirt was fouling an injector valve causing it to stay open and leak, maybe the Seafood cleared it?

Neil.



So my apologies for putting Seafoam in before checking for an injector leak. People were kind enough to help and some may've wanted to see the "smoking gun". (fault)

So far, I haven't been able to re create the issue. I think the Seafoam worked? However. The issue was bugging me and folks put time into helping with this so I thought I'd at least check the injectors for leaks, engine cold and post some pics.

No leaks found at injectors, spark plugs are very clean. Top of piston in cylinder 2 appeared wet but that could be due to the engine stopping just before that cylinder fired?

edit: since the fault occurred after the engine was brought up to temp, and since I didn't want to test the injectors when the engine was still hot, it occurred to me that it might be possible (ok) to submerse the pintle end of the injector in hot water, may 130º F ? then pressurize the injector with air and look for bubbles. But maybe that's just "crazy talk". Wink


All set up. Ran the pump for 5 minutes, no leaks at injectors. Same result pump off and injectors exposed for at least an hour.




Image may have been reduced in size. Click image to view fullscreen.




#1 injector closest. I even left a paper towel under them. No stains.



Image may have been reduced in size. Click image to view fullscreen.




plugs look super clean, as they should be. Engine is at about 1000 kilometres



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PostPosted: Wed Dec 19, 2018 5:48 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

crazyvwvanman wrote:
To see if a fuel injected engine won't start because it is badly flooded, try quickly unplugging the injector wiring plugs when the problem happens. Leave them unplugged and then try to start again and see what it does. If it briefly starts or tries to more than before that will confirm the presence of extra fuel. This should clear out the fuel and let it start again when plugged back together.



So I realize this isn't the same diagnostic process but today, engine hot, it wouldn't start. Exactly as it has done before, on two start attempts, it would catch but sputter and die. After I disconnected the fuel pump, it started normally then gradually stalled. Re-connected the fuel pump, it started and ran normally.

I'm not certain this means I'm dealing with excess fuel at start up but it seems to prove that I'm dealing with a fuelling issue.

edit: another set of no starts. Disconnected fuel pump, still no start after several tries. Bypassed fuel pump, ran pump for 5 seconds, it started normally. Intermittently failing residual pressure valve in pump? This is driving me nuts!

Neil.
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PostPosted: Wed Dec 19, 2018 7:54 pm    Post subject: Re: Fuel Pump vs ECU relay: Intermittent failure feels different? Reply with quote

Hi Niel. The answer is yes. You are leaking fuel into the cylinders and there is no pressure in the lines (probably intermittently). On other antique fuel injection systems I operate don’t have provisions to keep the fuel pressure in the system. You shut them off the fuel boils in the fuel injector lines and floods the engine. Now you go to start it and it is sort of flooded and has no fuel at the same time. On those engines the trick to starting them hot is you have to get fuel back into the fuel system witch really floods it then you start it with full throttle. So how does this relate to your van? Your engine is flooded but still has no fuel pressure. You have clear the engine then get fuel back in the system before it will start. The new fuel injectors will stop the flooding of the engine but I think you have a internal fuel leak as well (the pump or the fuel regulator). I am sure you could figure out a way to start it. But I think you have two problems not just one. Just my guess. John
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