|
||
|
26th July 2016, 08:37 | #1 |
Avid contributor
MG ZT-T+ Join Date: Jun 2014
Location: Guildford
Posts: 143
Thanks: 8
Thanked 20 Times in 13 Posts
|
Power Issues Under Load - Diesel
Hi All,
I’m hoping you can help me. I’m having an issue with, I believe, fuel pressure on my car. When the car is warmed up (also happens when cold but not as early) if I accelerate hard it revs to around 2500-3000 and then jerks and loses power. If I come off the power a little it starts to accelerate again, but if I boot it the same thing happens again. Providing I’m gentle with the throttle it doesn’t happen. The car revs fine in neutral however, when accelerating or if under load such as a very steep hill where it needs a little more power it happens. It feels like the car loses all power then it tries again and again if I keep my foot hard down. It’s definitely related to load because if I happen to be doing exactly the speed limit J on the motorway once it gets to a speed where the engine is under a similar load the same thing happens. Now a little while back PhilT4 told that the pressure on my high pressure fuel pump was a little on the low side, nothing to worry about but just bear in mind. This sounds high pressure fuel related to me, but some other opinions would be great. If so am I looking at a replacement or rebuild kit or something else entirely? The two other fuel pumps (being an early diesel) have both been replaced according to the service history and I’ve tested both a little while back so I don’t suspect those initially but open to offers of advice. This has been going on for some time, but has been much more noticeable with the hot weather. Sorry for the essay. Ollie |
26th July 2016, 09:44 | #2 |
I really should get out more.......
Vauxhall Insignia CDTi; MG TF 135 Join Date: Jan 2010
Location: Norn Iron
Posts: 2,958
Thanks: 942
Thanked 378 Times in 297 Posts
|
Wouldn’t be your MAF would it? Somewhere in the bowels of my memory is an idea that the ECM refers to it most from around that rpm range.
I could be talking bolleaux, but you could try unplugging it and see what difference it makes, if any… Essays are good
__________________
Past cars: MGB GT; Escort 1300 Sport; Vauxhall VX4/90; Marina Coupe TC; Celica ST (1972); Montego Turbo; Astra GTE 16V; Astra GSI 16V; Golf GTI 16V (Mk II); Sierra XR4x4 Estate; BMW 325i (E30); BMW M3 3.0; BMW M3 3.2 Evo. Left some of the more embarrassing ones out. And about 30 motorbikes. |
26th July 2016, 10:09 | #3 |
Avid contributor
MG ZT-T+ Join Date: Jun 2014
Location: Guildford
Posts: 143
Thanks: 8
Thanked 20 Times in 13 Posts
|
Ah apologies, should've mentioned that. I had issues with MAF some time back and it's been unplugged since.
Just caused sluggishness. This is a very sudden jerk, loss of power which repeats itself every second or so if you leave your foot on the power. Pretty different to the MAF issues I've had on this, and other cars but thank you for your response. Ollie |
26th July 2016, 10:56 | #4 |
This is my second home
Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009
Location: Hampshire
Posts: 11,548
Thanks: 3,470
Thanked 3,119 Times in 2,247 Posts
|
Might be a fault on the low pressure fuel supply side - if you get a drop in HP fuel pressure the engine shuts down.
Try it with the LP fuel pressure sensor unplugged - it is the one on top of the fuel filter. |
26th July 2016, 14:54 | #5 |
Avid contributor
MG ZT-T+ Join Date: Jun 2014
Location: Guildford
Posts: 143
Thanks: 8
Thanked 20 Times in 13 Posts
|
Thanks Mike, I'll try that tonight and come back to you.
Ollie |
26th July 2016, 15:47 | #6 |
MG ZT Join Date: Jan 2011
Location: Newcastle Upon Tyne
Posts: 20,151
Thanks: 3,565
Thanked 10,837 Times in 5,718 Posts
|
worth doing a leakback test on the injectors first and foremost
Brian |
26th July 2016, 20:50 | #7 |
Premium Trader
75 CDT Tourer,2.5 Launch Saloon, Omipro MG/Rover (T4) Join Date: Jul 2007
Location: Liversedge, West Yorkshire
Posts: 5,405
Thanks: 1,105
Thanked 1,340 Times in 661 Posts
|
Yes I'd be looking at doing a leakback test on the injectors too
Russ
__________________
Replacement Key Service http://https://the75andztclub.co.uk/...d.php?t=244732 Full T4 Testbook diagnostics available. Diesel ECU repair and replacement. Options enabled or disabled as required. Diesel X-Power 135 and 160bhp, Rover 1.8T 150 to 160 MG 160 V6 to 177 upgrades available P.M. for details. |
27th July 2016, 02:01 | #8 | ||
Give to Learn
Freelander 2 Join Date: Aug 2010
Location: West Midlands
Posts: 18,714
Thanks: 1,155
Thanked 6,407 Times in 3,874 Posts
|
Quote:
In your knowledgeable opinion which or what is the correct way to do a leak back test. From cold and run for 2 minutes if so when does the time start as soon as fuel enters the leak off tubes, or when the fuel starts dripping into the containers. Am I right in saying that 20ml over that period of time is acceptable, I know what we would all like to see is none. Couple of videos below for the OP to watch and you also please, hopefully this will give members a definitive answer as to how these teats should or should not be run. Timed from when the car was started and fuel flowing into the tubes, video is for 1 minute as it took a minute for the fuel to flow up the tubes to top of the containers. https://youtu.be/WfTUFhjOZyQ Second test the next day timed from starting the car and fuel entering the leak off tube kit, total time 2.02minutes. https://youtu.be/VnGs_da2o Third Test same day right after the second test but this timed from entering the container as fuel was already in the tube, total time 2.08 minutes. https://youtu.be/mcoUSIjus I later ran an Hawkeye test on the injectors and they were within tolerance, have seen worse
__________________
Arctic Givology Learn to Give Everything is Achievable ad altiora tendo. Check out our Nano meet dates http://www.midlandsnanomeets.co.uk/ http://www.the75andztclub.co.uk/index.php?thepage=howto " You do the work , we supply the expertise " Last edited by Arctic; 6th July 2017 at 12:55.. Reason: spelling |
||
27th July 2016, 07:33 | #9 |
Avid contributor
MG ZT-T+ Join Date: Jun 2014
Location: Guildford
Posts: 143
Thanks: 8
Thanked 20 Times in 13 Posts
|
Thanks chaps.
I tried unplugging the pressure sensor and initially I thought that it had made a difference and that the problem only starting kicking in at around 3500 revs however, on the way back home after a little brake it was back to the same 2500-3k. I'll look up how to do leak back test and do that and report back, it may be some time as I'm pretty busy but will let you know. I assume this will indicate faulty injectors and therefore replacements with new or recon or good second hand? Thanks, Ollie |
27th July 2016, 07:39 | #10 |
Posted a thing or two
Mk1 ZT 190 - Mk2 ZS 180 - Mercedes E63 AMG S - Ford Ranger Hawk Join Date: Mar 2016
Location: Middlesbrough
Posts: 1,456
Thanks: 123
Thanked 409 Times in 281 Posts
|
Running without a MAF is not ideal, replug in the MAF and try again see if it does it, your MAP sensor could be shot or dirty causing it to lose power on boost as thats the sensor it relies on when the MAF is bad.
Personally i'd have a new MAF fitted or get a good second hand one, without the MAF your on base values and really isnt ideal for the engine.
__________________
http://i66.tinypic.com/5cd6xj.jpg |
|
|