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Discussion Starter #1
Hi
I have a couple of P38 diesels and I suspect one of them might be developing a fuel pump issue. Reading codes I get code 136, fuel actuator circuit fault. Also once in perhaps 10 times you dip the accelerator at idle it will almost run away (1600-1800 RPM) and then almost stall (500-600) for a fraction of second before settling into a steady idle. Runs fine otherwise.
This has led me to read up on rebuilding or replacing the fuel pump. I see rebuild kits on eBay that include gaskets and washers of various sizes, but I suspect this is just for leaking pumps and not a complete overhaul which from what I understand is not possible for a DIY'er.
Do these pumps tend to wear out? And usually when do they? My P38s are at 220' and 235' km (2000 models).
When they wear out, is replacing with a new or recon/rebuilt unit the only solution?
And would you recommend doing the timing chains if fitting a new pump?
 

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Hei.

There is a feedback sensor on the fuel actuator solenoid. If that circuit does not work correctly the ECU might turn the actuator too much and then regulate incorrectly back to idle. I'm only theorizing now after extensive reading of the electrical schematic circuits surrouing the fuel injection. The fourth injector sensor is also related to that circuit.

As far as longevity I've only had mine for a year but it came with a leaking top cover, actuator solenoid housing or whatever it's called.
As far as documentation with the car the pump was the original one. I replaced it at 355.000km. Only fault was the leak a hot start issue so previous owner installed hot start fix. That could be because of a slack in the timing chain or worn pump.
My "new" pump has 150.000km. I set the timing to 0,95 according to the manual. The only thing I can complain about is idle is a tiny bit rough when engine is cold.


You could always speak to Göran who runs Dieselmeken in sweden. He is a reputable diesel pump specialist. Mostly known on the internet for serious tuning of the Bosch M-pumps on mercedes diesels.

http://www.dieselmeken.se/kontakt


There is also a user on landyzone.co.uk that has done lots of work on the P38DSE. Whammer or whammy I think he calls himself.

// Benjamin
 

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Oh, one other thing.

Regarding wear on diesel pumps, changing filters and running fuel with low water content is essential. Luckily we have a good quality fuel in Europe. Once I heard from a friend who was working in New Zealand at wintertime with snow cats, where they had big problems with the engines with high combustion temperatures, Cummins in this case, where injectors failed and the engines needed new pistons and sleeves. The same engines ran totally fine in Sweden.
All this due to their inability to source a high quality diesel fuel. The fuel they got had 23 times(!) the water amount that is ok according to the standards we use in europe.


// Benjamin
 

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Discussion Starter #4
Hei Benjamin!

Thanks for the tips. The feedback actuator solenoid, would that be the black part mounted on the side of the pump with a cable running from it. Or is it internally in the top of the pump?

IMG_3201.jpg

No it's not leaking. That's just brake cleaner to decode the part number.

Both of mine have the hard hot start "feature" and have for the past two years of ownership.

Thanks for the contacts. Those might be handy. I'm currently doing a lot of work on this P38 (front diff, exhaust, leaking oil filter cap etc) but hope to get plates back on it after easter, but I hope to avoid replacing or rebuilding the fuel pump right now.

By the way, did you get all the speciality tools to perform the pump change and set the timing when you did yours?
 

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Yes inside that housing is the fuel quantity servo unit and the rotary potentiometer that gives feedback to the ECU how much fuel is injected.

I bought the toolkit to remove the pump from the pump gear without dropping the pump gear in the timing case. https://www.ebay.co.uk/itm/Fuel-Injection-Pump-Puller-Hydraulic-Valve-Lifter-Tool-Kit-Set-BMW-Land-Rover/262824414146?hash=item3d318e4bc2:g:U~0AAOSwBLlU5oQv

And also the dial indicator gauge kit. It did not work for me out of the box. I had to modify the tube that scews on to the pump. Make it longer and also make my own rod that goes in the tube between the gauge and the pump. Good thing is that I can now mount it without removing any injector lines. Kind of handy.

https://www.ebay.co.uk/itm/VW-Audi-Seat-DIESEL-FUEL-INJECTION-PUMP-Stactic-Timing-Adjustment-Gauge-Tools/222557421527?hash=item33d174bfd7:g:WMcAAOSwDrNZTk6Y



I made a big mistake when I replaced my pump. I started a thread about it here.
Basically the first mistake was I did not bleed the replacement pump enough and the engine would not start.
The second one was during swapping the old pump back and it went weeks before I realized I did not get the pump shaft correct. The wood ruff key was a couple of mm to the side of the slot. Timing was totally off.

But after that was sorted out everything worked great.
 

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Discussion Starter #6
Thanks for these awesome tips.

Do you know if removing the black solenoid device would disturb timing or any setting of the pump? I'll search around a bit but thought I'd ask in case you knew.
 

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Hold on a minute. I did not mean in the black part but the aluminum housing it is mounted to.
That's where the fuel servo unit is.

That housing has a calibrated position which if moved the fuel quantity is no longer correct. If the screws are loosened a bit and the housing is moved forward equals more fuel. Backwards, less fuel. There is a hack job called the hammer mod on these pumps. You'll have to google it if that sounds interesting.

Take a read through the rave manual.
Both the workshop manual and the electronic troubleshooting manual has lots of information on the pump.

Timing device is in the bottom of the pump.
 

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Here is a useful guide on overhauling the Bosch VE pump:

https://www.vwdieselparts.com/forum/viewtopic.php?t=6694

Not quite the same as the p38 version but similar.

Bosch fuel injection pumps usually have a long life (or maybe used to have a long life). In Europe sulphur has been taken out of diesel for environmental reasons and this acted as a lubricant in the fuel.
 

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Yes inside that housing is the fuel quantity servo unit and the rotary potentiometer that gives feedback to the ECU how much fuel is injected..........................

.............................
The second one was during swapping the old pump back and it went weeks before I realized I did not get the pump shaft correct. The wood ruff key was a couple of mm to the side of the slot. Timing was totally off.

But after that was sorted out everything worked great.
can you elaborate on this. If the pump sprocket is set correctly with timing marks aligning, you can't miss timing. The pump key would slot in the right place , you can'y put it in otherwise.
 

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Thanks Dave! That's a great guide and help. I also came across this guide on the net. Very similar:

http://quietglow.com/dieselvanagon/Bosch_Pump/-Rebuild

I hope the pump holds up a while, but I'll start to look for parts and/or a spare pump that I can tinker on and have handy. But today my primary P38 broke down and won't start (electrical). But that's another story for another time.
 

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I was curious to how the solenoid housing looks on the inside. I took my old leaking pump and opened it up to see and took some pictures.
IMG_3206.jpg IMG_3208.jpg IMG_3209.jpg IMG_3210.jpg IMG_3212.jpg IMG_3213.jpg

By the way I got a fact wrong earlier. I wrote that this housing is pushed forward in the direction of travel to increase fuel and vice versa. It's the other way around.
So to increase fuel and idle. Loosen the scews marked with red in my picture and lightly tap the housing backwards with a piece of wood.
Forward to lower fuel and idle.

P38 - Diesel Pump

You can read the post of Wammers how to easily set up the fuel/idle after this housing has been removed. Sounds pretty straight forward.
 

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If it's throwing faults(and incorrectly responding to throttle pedal), then actutator magnet is probably full of metal shavings, common problem with this pumps, this can be cleaned, but you have to strip it completly and then solder or crimp some connections
 

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can you elaborate on this. If the pump sprocket is set correctly with timing marks aligning, you can't miss timing. The pump key would slot in the right place , you can'y put it in otherwise.
Hello I did not see this question earlier.

You are totally correct, it should not be possible. That's what I thought too before I realized what had happened.
During pump swap I missed the slot by a couple of mm and drove the pump shaft onto the pump gear cone with the nut.
Result: Timing extremely retarded. Hard to start, lots of white smoke and no idle.
When I decided to swap pump again I realized my mistake when noticing how few threads the nut was screwed on to the pump shaft.
So I removed it and looked at the wood ruff key. It protruded very little from the conical pump shaft. Quite a big difference when comparing it to my other pump I wanted to use.

I see you still haven't sorted out your problems with engine timing?
 

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Thanks N2O. I'll probably strip it down completely and clean it and fix it up in time. Good tips that sounds like the issues I am developing.

And thanks kretslopp for the tear-down. I have been curious about the insides and details myself, so it was nice to see the pictures.
 

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Removed the front cover and checked timing (No. 1 cyl at TDC and crank locked), it is spot on.
My car starts on the button when cold but when hot , it's a pig.
I have never taken the inj pump out. But got to check that too as my timing modulation is at 94, most of the time.
 
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