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Go Back   TDIClub Forums > VW TDI Discussion Areas > Alternative Diesel Fuels (Biodiesel, WVO, SVO, BTL, GTL etc)

Alternative Diesel Fuels (Biodiesel, WVO, SVO, BTL, GTL etc) Discussions about alternative fuels for use in our TDI's. This includes biodiesel WVO (Waste Vegetable Oil), SVO (Straight Vegetable Oil), BTL (Biomass to Liquid), GTL (Gas to Liquids) etc. Please note the Fuel Disclaimer.

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Old February 20th, 2020, 04:42   #1
bogno
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Default 1.9 PD Tandem pump, fuel in oil adventure

Hello All. There are two parts to this post, a cautionary tale and an unfolding question.

First a quick intro: I enjoy a bit of hobby mechanics, and have been playing with our 1.9Tdi PD 2005 Caddy. It's been re-mapped (was before we acquired it at 47kmiles, so don't know the details, but when you put your food down it goes!).

At 140k, I decided it was time to dabble in running it on straight veg oil and began a two tank conversion. We produce a youtube channel, called Flowering Elbow, and thought it might be an interesting thing to share with our subscribers there… To cut a long story short, we recorded the conversion process, got the van up and running, did 500 miles (in two long trips).

Then we did a few short 1-2mile (diesel powered) trips, the last of which there was an audible bang on startup, but ran fine… Before a serious problem…

Starting on diesel, we noticed more smoke than normal. Should have stopped then, but my wife had urgent appointment. Drove very cautiously - basically idling through town, got to a hill, low power, engine suddenly increased noise, plume of smoke Luckily there was a place to pull over right there and I cut the engine quite quickly, after noise increase. We got toed and my wife never made her appointment

Upon Investigation: There was fuel (diesel) in the oil. Lots of it! When I drained the sump, there was about 12L of oil-diesel in there. So I guess hydrolocking may have been a thing? There was also about 1l filling the pipe from turbo to bottom of the intercooler.

My Theory: The lift pump for the new aux diesel tank was too high pressure. I was working from the assumption that the tandem pump would regulate pressure and send any unused fuel back along the return line. Of course the tandem pump may have just failed anyway... But I strongly suspect my lackadaisical testing of the new diesel pump and feed pressure causing tandem pump to blow seal between fuel and oil?

How bad is it?: Pulling the sump, I haven't found any debris, and the bottom of the connecting rods an crankshaft look ok (to my untrained eye). If a connecting rod was bent is there a way to tell by looking?
The turbo looks surprisingly ok? At least the turbine blades seem intact, if oily, and I can move it by hand without huge amounts of play – although, again, I don’t know how much play is unacceptable?



Looking behind the valve cover, I see quite a bit of wear on the cam shaft (I guess that’s expected when you lube it with half and half diesel-oil right The chamfer on the sides of the lobe peaks is worn and I can feel a burr there. I can’t see how worn the lifters are until I have the shaft out, so I don’t know if I have any holes in them yet…




And so, my questions to you: I think the tandem pump was the problem, but equally, fuel could be leaking round the unit injector O-rings (but maybe not in that quantity?) Either way I may as well have the unit injectors out and get them tested / new seals…

A new camshaft kit is £360, new tandem pump £240. I have the option of getting a new (to me) engine inc. tandem pump, camshaft turbo, and injectors that’s done 85k for £610… I don’t know what to do – try with new parts which should last longer assuming cylinders ect. are ok. Or just get the whole engine and then if injectors or some other bit is bad, I can replace…

What else should I be looking at with this? What other obvious components that might have failed due to oil dilution / over volume?

Thanks friends,
Bongo.

Last edited by bogno; February 25th, 2020 at 02:01.
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Old February 20th, 2020, 07:04   #2
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Do us all a favor and post smaller pics (800x600) so as not to blow the margins out on the pages. It makes reading the thread hard as you have to now scroll back and forth just to read it. You can post a clickable thumbnail with a small pic that when clicked on links to the larger high rez pic if needed. Good luck with your issue and welcome to tdiclub!
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Old February 20th, 2020, 07:19   #3
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Hi Lightflyer,
You got it. I see that now I an looking at it... Will try and edit the post to correct it when I get back to my desktop.
Thanks for the welcome

A small update: I got a glow plug out and it seemed in surprisingly good condition. I half expected there to be a flow of oil out the plug hole...

Last edited by bogno; February 20th, 2020 at 15:38.
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Old February 20th, 2020, 16:26   #4
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I am far from an expert on the PD (or anything else), so take this with a large grain of salt. But I wouldn’t think too much lift pump would cause this. You will only get fuel in the cylinder when the injector is firing, and the bit of extra LP pressure shouldn't make a difference. Generally, I would blame this on an injector stuck open, allowing the fuel to flow constantly. Have you ruled that out?

Once the cause of the diluted oil is corrected, I might be tempted to bolt it all back together and just see how it runs.
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Old February 20th, 2020, 19:21   #5
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Looks like you may have some dreaded cam wear as well. That lobe that is up seems to have lost all of its bevel from around the edge up towards the top.
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Old February 21st, 2020, 01:18   #6
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Hi Philngrayce. I thought that about thr lift pump too.
A unit injector stuck open is an interesting possibility. I didn't know that was a thing... I will have to have them out and sent off for testing. Anyone know how I might go about bench testing the tandem pump for oil to fuel leakage?

@Lightflyer well spotted, yes. I think a new cam shaft and lifters are in order. Just tossing whether it would be best to get a whole engine... ?
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Old February 25th, 2020, 10:17   #7
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Default Unit injectors out!

An update. I had the unit injectors out today. Not easy - they were in there tight! I ended up wrapping some webbing round them, tying it to a long leaver and using it to pull them out

Now I need some help interpreting what I am seeing:





The tips are quite blackened and crusty - a lot of which comes off with a firm wipe off with paper towel. Unusual looking for 140k miles?



Upon removal - there is a band of fuel between the small o-ring and the middle o-ring (does this indicate fuel leaking past?)



Once wiped down I can see quite a bit of wear along the body here, where the anodising has rubbed off. Significant

Does anyone know of anywhere good in the UK to get the injectors tested?

Assuming similar crud build up has occurred round the piston rings, now I have both the sump off and the injector ports open - what would be a good thing to squirt in there to try and break down/flush away that stuff? Would carb cleaner be a good option?



In other news I also had the throttle body and ERG off to look at (and as it turned out clean ). As you can see, before the ERG valve entry, things are relatively clean. After ERG entry, things start to look like the bottom of a student oven...




From what I have read this is normal for this kind of milage, and I probably should have cleaned it out a while ago, can anyone confirm?
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Old February 25th, 2020, 13:33   #8
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How many psi was your add-on lift pump running?

The injectors are lubricated by engine oil (so there is a fuel/oil interface, per the two o-rings) but in general oil pressure >> fuel pressure, which is why a bit of oil leaks into the fuel normally and why the inside of the fuel tank eventually turns black.

I suppose a really strong lift pump would mean fuel pressure >> oil pressure and reverse the flow direction.

Just a theory.
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Old February 25th, 2020, 17:48   #9
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Would not be the first time I've had a tandem pump spew fuel into the head and thus the rest of the engine.

The injectors I commonly see the bottom o ring compromised, but that won't fill the crankcase, though may be the primary cause of why you commonly see black soot in PD fuel filters and the rest of the fuel system.

The top o rings are exceptionally rare to see any failures from, and those are what seals the pressurized fuel from the rest of the head.

Also, the high pressure feed into the injectors is between the bottom red o ring and the middle o ring. The return side, which will be significantly lower pressure, is between the two black o rings. The pressure there is low enough to where it would be really strange to see fuel working past that upper o ring and into the head.

The tandem pump input shaft seal is what will generally cause the fuel contamination into the head. I've replaced more than a couple tandem pumps for this.
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Old February 25th, 2020, 18:17   #10
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Quote:
Originally Posted by Matt-98AHU View Post
The tandem pump input shaft seal is what will generally cause the fuel contamination into the head. I've replaced more than a couple tandem pumps for this.
Makes complete sense...great post.
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Old February 26th, 2020, 02:20   #11
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@Vince Waldon, that's a really interesting thought thanks. It's going to sound stupid but I'm not actually sure what pressure the new lift pump was making. I will test and get back to you...
Matt, thanks for this, great info in regards to the unit injectors. I do suspect the tandem pump was the problem. If I take it apart on the bench, will I be able to spot 'by eye' if the shaft seal is gone? Is there another way to test it on the bench? Anything specific to look out for?

Matt, do the tips of the injectors look excessive to you? Any thoughts on what might be best to flush out the cylinder area with / what dissolves the black deposits but wont attack the alu head or cast iron cylinder?
Thanks for the replies guys, keep em coming
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Old March 1st, 2020, 03:24   #12
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How long did you drive with the oil/fuel mixture? I put in a new tandem pump that from factory had a failed seal inside and within 2 days I had 10L in my oil but my oil light went off and I pulled over. I have 177,000km and my cam, turbo and injectors look nothing like that (all of which had a peak at after failure). I also still had good power. I can't speak to the other work you've done, but something else is probably causing your failures unless you ran for weeks like that.
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Old March 2nd, 2020, 04:44   #13
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Hi Wrekked. Thanks for the info, really interesting. There was about 15L of oil/fuel mix - so way more diesel than fuel. No lights came on. I don't honestly know how long I was driving with it like that.

After pricing up just a few bits - good OE quality cam shaft kit and tandem pump, I was already spending more than a whole new engine. So I decided to go that rout in the end.

The new to me BLS engine has done 85k miles, was £550. I pulled the valve cover and had a look at the cam shaft which looks perfect. No leaks anywhere, nice and clean, came with the turbo that looks in good condition. A small amount of carbon build up round ERG & manifold, which I am cleaning up.
So yeah, I am quite hopeful
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Old March 3rd, 2020, 12:52   #14
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The oil light only comes on when running higher rpms. Iirc it won't come on until 3000+ rpm.

good thing with diesel is that it has some lubricity. If this were in a gas engine I'm sure everything would be toast.

I wouldn't be suprised if the other issues were caused by BIO, but I know nothing about that. Hope the new engine serves you well!
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Old March 26th, 2020, 08:16   #15
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Thanks WrEkkED. I just thought I'd follow this up with the continuing adventure.

So I installed a new e-bay engine (85k miles). So far everything is working well
I tested it on just diesel before making the plunge and running the 2 tank veg oil conversion again - this time with a reasonable fuel lift pump for the aux diesel tank. Only done about 100 miles so far. Now with lockdown, it might be a while...
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