Patrol TD42T injection pump problem

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Patrol TD42T injection pump problem

Unread post by nemoleon » July 20th, 2010, 3:34 pm


I have a strange problem with my mechanical injection pump in nissan patrol Gu4. Engine TD42T. In fact it is brand new engine TD42Ti, but I demounted the electronically steered TD42Ti pump and mounted mechanical TD42T after the full rebuild and factory set (I did it because I do not have the computer for TD42Ti pump so without it it is not possible to adjust the timing corretly).
The problem is with the slow revs. During the hot weather mostly the slow revs go down from 700rpm to around 400-500rpm without any reason, not frequently but once it goes this day it will stay low. The pump is after the full rebuild some 5.000km ago, and it was OK until warmer days come. I already rised the low-revs with the appropriate screw but it seems week by week it is getting worse and worse and there is no place for regulation anymore...
There is no problem on higher revs, no problem with the high speeds, it is reving OK, no lack of power. It's worse when the tank is nearly empty and a little bit better when it is full. I can't stop the car on traffic lights because it is extremally difficult to start driving after the revs go below 500.

All the filters are new, including the fuel and air filter. The fuel lines are ok, no leaks and air getting into the line. The A/C is disconnected to exclude this as a reason (anyway the A/C actuator works fine for rising the revs during the A/C work). There is no filter in the banjo bolt in the intake of the pump. I chcecked nearly everything what I know.

Do you have any ideas what's wrong? The difficulty is I'm in Poland and NOBODY knows anything about this injection pump at all I will send a huge pack of beer to AU to anyone who could help me
I'm so desperated that even thinking of mounting old TD42 (non turbo pump) to this engine. Will it work correctly?


Peter Aawen
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Joined: June 17th, 2005, 8:01 pm

Unread post by Peter Aawen » August 28th, 2010, 9:41 pm

Hi nemoleon, sorry this has gone unanswered for so long!! Firstly, what are your base level idle revs?? If they are set too low you may be having hassles due to that, so set them to at least 700 rpm - or it could be that the injector pump itself isn't getting enough fuel for whatever reason.

Check that you have no restrictions in the fuel lines or filters; that you are getting good fuel flow into the injector pump; & if you can get the transfer pump pressure tested or enhanced, do so! For those who don't know, transfer pressure is the pressure provided by the first stage of the injector pump, & if that's not up to speed then the second stage (the bit that sends/distributes fuel to the injectors) can't do it's job properly, giving symptoms like those you've described!

And there may well be a clogged or clogging filter under the fuel inlet banjo - we often see tiny little filters (about the size of your little finger nail) under that inlet connection that get clogged. They are about 40mm down inside the injector pump body once you've taken the inlet banjo off, so you'll need to use an engineers scribe or 'O' ring pick to reach down inside the pump & pull it out if it's there. It is often put in by the pump tuners as a last line of defence against debris getting into the pump, & they can easily be the cause of your problems, if fitted. So check to see if you've got one, & if so, clean it & replace it, or if you want to risk it take it out entirely (but if it's already clogged it's gonna be doing its job, isn't it??)

But tell me, has your injector pump been checked out/set-up properly?? That low rev difficulty is often something associated with worn or water damaged pumps from low quality fuel - they usually run OK if you can get them started & get the revs up, but starting/low rev issues (largely cos of that transfer pressure being too low) can make life a pain. Some people get away with adding a lift pump down at the fuel tank, so the 1st stage/transfer pump section of the injector pump doesn't hafta work so hard, and that can mean your pump is then able to do it's thing well once the revs get up; so it might be worth a try.

Apart from that, all I can suggest is finding somewhere that will rebuild the pump back to spec (or better than spec!) for you, & with any luck do some smart diesel tuning (better than the static timing set-up you can do with the engine stopped!) to maximise your power/torque & fuel economy without blowing your Exhaust Gas Temps thru the roof. I usually get our TD42's injector pumps, injectors, tappets, & tuning (& turbo's where fitted) done up by Cooma Diesel about once every 250,000 km or so, & you can really see/feel the difference in the way the engine performs. Well worth driving half way across the country (& in Aust that's saying something!!) to get it done by someone really good rather than just the best in the local area; and it pays for itself in driveability & fuel economy very quickly.

Hope you can get it sorted, Cheers

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Unread post by Roachie » August 28th, 2010, 10:06 pm

I agree with everything Peter has said, but would add this:

The first thing I would do, at a cost of under $100-, is to add a small 12volt lift pump near the tank (something like this: FACET SOLID STATE ELECTRIC FUEL PUMP 4-6 PSI FP40106N - eBay Fuel Pumps, Air Intake, Fuel Delivery, Car Parts, Accessories, Cars, Bikes, Boats. (end time 21-Sep-10 15:57:29 AEST)

At least this will help overcome any possible "supply" issues the IP might be having and it can also assist with ensuring the fuel lines are clear, by powering it up without the engine running and with the fuel delivery hose removed from the IP. Also good for bleeding after a filter change.
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