Intermittent power loss.

DaveC · Post by **DaveC** » 05 May 2004, 19:38

Hiya, I run a Pug 405 Tdi. Bosch pump and all.
Just curious if anyone here has evr had the following problem.
A few months ago I tuned up my fuel pump, but before then, the car had terrible lagging kind of power-loss now and again.
I couldn't work it out myself. Hard on the power, overtaking say in 3rd upto 60mph, and at about 3000rpm, the engine kind of looses 75% of the power. It doesn't black smoke at this point, just looses power, and accelerates very slowly, almost like I've hit maximum rpm, even though I'm at 3000rpm maybe.
I ran through Redex stuff for diesel engines a bit, put in new fuel filter, etc. I eventually took it to a diesel specialist and they tested the boost and all and said it was all in good order, just the intercooler seal was failing. They replaced that, and replaced the turbo boost compensation pipe from the intercooler to fuel pump.
The car did feel better, more punchy, but the harsh halt in power was still there!
I decided to try sort it myself, and reading about tuning I turned my pump up etc.
I've been running it since, with the problem only surfacing every 500 miles or so. Right now it's been doing it for about 300 miles, so I'm running some BP Extra fancy diesel and some Redex through again.
With it turned up, it's still very fast, right up until the engine suddenly stops pulling, and makes almost an empty revving sound like fuel starvation maybe.
Since it comes and goes I'm really confused, I'm beginning to think it's the maximum revs adjustment is far too low, or maybe there is an intermittent blockage in my whole fuel line.
Either way, has anyone had a similar problem? It really is noticeable, accelerating to 60 in 3rd, get to 45mph, looses power (sometimes), and then just runs sooo slowly upto 60mph but about 3 times slower than usual, making a noise like it's really struggling.
Sometimes it doesn't do it at all, and other times it kicks in just before 4000rpm.
Then if I change gear to 4th at this point, it lags a second, and then pulls hard again, and then hits the power-loss band again.
Really weird...
Does anyone know how to adjust the maximum rpm on the fuel pump. I've heard it mentioned, but don't know where or how to adjust it!
Or, has anyone had this kind of problem and found it to be an iffy fuel line blockage?
It really is a shame, since when it's on full chat and not doing it, the car feels so much faster as I can hold onto gears for longer and really appreciate the power!
PSPS, I did a 0-60 test on a flat road, got 12.8 seconds with this power-loss happening. My brother who tuned his up like mine, but doesn't have this problem, got 8.6 seconds. We timed them both the same, so they are relatively equal to each other. I just don't understand how his can be 4 seconds faster... thats like 40bhp more required to accerate that much harder.
Either his car has the boost turned up higher (did a hybrid engine swap with a Xantia TD and just "set" the wastegate level length by eye), or my car has got major power-loss at the top end when this is happening!
Hmmmmm
Cheers for any help!
Dave

AndersDK · Post by **AndersDK** » 05 May 2004, 21:54

Dave, check your exhaust for any internal debries blocking off the exhaust. Thumping the boxes & pipes you may be able to hear any debries rattling around.
Even a minor restriction would promptly slow down the turbo, and then it's goodbye engine pulling, as the turbo relies on exhauast gas flow.

DaveC · Post by **DaveC** » 05 May 2004, 22:07

Hmmmmm, interesting!
It's funny as I notice some stupid things sometimes, and one of them is when ragging it up a particular slip road on my way home, which is a long left hander, the problem almost never occurs, and then as I straighten out up the slip road proper, it looses power.
Now I don't know if thats just me, or if pressure is generated in the fuel line, or if the wastegate is held closed a "teeeny" bit more or what.
Debris could be the problem if it's blocking a silencer exit. I'd expect the back pressure would kill a turbo impeller speed.
Mind you, always at a certain rpm range (3000-4000 ish rpm)...
I'll have to take a look and bang about when I do my front ARB bushes!
Cheers
Dave

AndersDK · Post by **AndersDK** » 05 May 2004, 22:19

Also check the fuel tank is vented OK [;)]

JohnCKL · Post by **JohnCKL** » 05 May 2004, 22:22

Is it possible the clutch is slipping? Time to renew the clutch?

DaveC · Post by **DaveC** » 05 May 2004, 22:35

I think the clutch is ok. I've been doing lots of 0-60's and stuff and it seems to grip well enough to spin my Toyo Proxes.
Seems to be when torque has peaked and it's getting upto 3000 rpm, then it just goes, which is why I think it fuelling maybe. If air blockage was a problem, it'd smoke (over-fuelling to air coming in). Mind you, if it was dropping boost, maybe a dodgy wastegate, the boost compensator would reduce fuelling, so it wouldn't smoke then. Mind you, if it lost boost, it'd be more likely at peak torque maybe? Mind you, peak boost is at 3000rpm, so maybe the wategate opens at 3k, and stays open sometimes!!!!
Hmmmmmmm!!! Think thats it maybe now, hehehe!?
Oh well, loads to check on my list now [|)]
I'll have to get myself a boost gauge!
Still, I think a good fuel tank and fuel line service/check would be good to do.
Cheers
Dave

Post by **philhoward** » 05 May 2004, 23:04

Silly thought....if yours is a 1.8TD, is it like the BX TD and there's an overboost switch? What does that do to things?

bernie · Post by **bernie** » 06 May 2004, 00:17

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by philhoward

Silly thought....if yours is a 1.8TD, is it like the BX TD and there's an overboost switch? What does that do to things?
<hr height="1" noshade id="quote"></blockquote id="quote">
Where and what is this "overboost switch" on a BX TD?[?][?]

Post by **philhoward** » 06 May 2004, 00:20

Just remembering something i've read on other posts...I think! There's a light on the dash for them, anyway, or is that just it?

bernie · Post by **bernie** » 06 May 2004, 00:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> There's a light on the dash for them, anyway, or is that just it?
<hr height="1" noshade id="quote"></blockquote id="quote">
When I did the water temp. guage mod on my BX TD TZD 1992 there was no lamp or wiring to said warning lamp on the binacle[?]

Post by **philhoward** » 06 May 2004, 00:48

OK, my mistake...sorry!
Perhaps i'm thinking of XM Petrol turbos instead...
(Been a long day..)

bernie · Post by **bernie** » 06 May 2004, 01:23

No problem Phil[:)], I just thought you found something my BX should have[:(]

Post by **RichardW** » 06 May 2004, 12:49

No, Phil, you are not dreaming! Some BX TDs were fitted with an overboost switch. It was loacated somewhere under the battey and had a thin feed line teed off the boost compensator line. If it activated on high boost presure (not sure what it was set at) it lit an orange light in the top right hand corner of the instrument panel (the one next to the 'picture' of a turbo, funnily enough!). My '88 had one, but I don't think the '91 did. Worth checking the hose is intact if fitted to avoid losing that all important boost!!

DaveC · Post by **DaveC** » 07 May 2004, 18:15

Hmmmmm, this problem seems to be stopping again. I've been accelerating hard again and revving to 4000rpm without much trouble. Just the odd tiny little pause in power!
Maybe the Redex is doing the trick. I think a full fuel line and fuel tank clean is in order, then I can rule out everything but the fuel pump and injectors.
I've heard that the lever arm controlling the throttle on the Bosch pumps can move up and down, when the bearing and seals wear where the lever pivots inside the pump. Apparently it can let air in, and I was wondering if at high rpm, when the pump is sucking harder, it might begin sucking in a bit of air, ruining the fuelling a bit.
That might be why cornering and hard throttle stops it, as the fuel is under pressure inside the line, and air doesn't bleed in.
The guy at Powerline in Shipley said it was on it's way out a bit, and was £125 to sort out with new seals and bearings and re-timing.
I suppose if all else fails then it must be that!?
Cheers
Dave

Post by **philhoward** » 07 May 2004, 20:02

That's normally the difference between the Lucas and Bosch pumps; the Lucas one fall to pieces; the Bosch ones don't...as a rule, but there are always duff ones..
I thought you said you had the Bosch pump?