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Some tips on diagnosing and rectifying Diesel related faults

56K views 49 replies 39 participants last post by  Diggy05 
#1 ·
.Checking for Air ingress

1. Obtain some 8mm id clear pipe (aprox 3 ft should be plenty) and suitable hose clips (6)

2. Replace the black nylon pipe going from the filter housing to the fuel pump.

3. Run engine for 5 to 10 min then observe the pipe, a couple of small air bubbas every minute is acceptable but anymore indicates a problem so read on.

4. Now disconnect the fuel heater from the steel supply pipe and the filter housing with clear pipe and repeat step 3. If air bubbles disappear or are reduced this indicates a problem with the fuel heater and requires replacing.

5. Now connect a piece of clear pipe from the steel feed pipe that should go to the fuel heater direct to the fuel pump and repeat step 3. If you still have lots of air bubbles chances are there is a problem with the flexible pipes at the fuel tank, but this no very common. If the air bubbles have gone you also have a problem with the filter housing and requires replacing.

Checking glow plugs

· Connect a test light / multi-meter (set on DC volts) to the glow plug bus bar and switch on ignition, Check voltage should be battery voltage. Observe the dash warning light for glow plugs when the light goes out the plugs should stay powered for several more seconds.

If no power check the fuse an 80A fuse located in the fuse box next to the battery. Check this carefully!!! As the fuse is know to fracture and this can be very hard to see through the little window It is best to prise off the window and carefully check the integrity if the fuse. If the fuse is ok suspect the controller.

· Remove all 4 glow plugs and connect using suitable sized cable to a battery and see if they glow (be careful NOT to hold the plugs whilst testing or for at least 10 - 15 mins after testing as they get VERY hot. If any plugs fail to glow replace the set not just the fault ones with good quality plugs.

I would advise against purchasing cheap or unknown brand glow plugs, as I have known them to fail after only 1 day the main culprit being a brand called Wellman. The best available are Beru, Delphi, and NGK.

· Whist the plugs are removed check the integrity of the bus bar if faulty replace

Fault diagnosis

Problem

· Car lacks power

· Sometimes revs up without actuation of accelerator pedal

· Increase in fuel consumption

Possible cause

· Split boost diaphragm

Diagnosis

· Remove tapered pipe from boost box on the side of the fuel pump (front as you look at it facing the radiator) and check for presence of diesel fuel

Remedy

· Replace boost diaphragm

· Some people will tell you that it is possible to change in situ but this is not recommended as once disturbed the fuelling will be out of calibration and will need resetting on a calibrated test bench

Fault

· Uneven idling, presence of blue smoke from the exhaust, poor drive ability

Cause

1. Faulty advance solenoid

2. Needle lift sensed injector

3. Throttle pot

Diagnosis

1. Have an assistant switch on the ignition whilst you listen close to the fuel pump. You are listening for a series of evenly spaced click's, if not present or uneven solenoid replacement will be required

2. With the engine and ignition switched off disconnect the plug from the injector and check the resistance across the terminals the reading should be between 95 and 110 ohms. If not replace injector

3. With the engine switched off mark the position of the throttle potentiometer that is located on the top of the fuel pump above the throttle lever then carefully loosen the 2 torx screws. Start the engine and move the potentiometer until the engine runs smoother if no improvement is possible or any of the cables are in poor condition where they exit the potentiometer replace with a new component.

Fault

· Excess black smoke from the exhaust

Fault

· Blocked air filter

· Faulty EGR valve

Remedy

· Check and replace if necessary the air filter element

· Locate the EGR valve (Mk1, under the intercooler follow the black vacuum pipe from the control valve on the nearside inner wing just near the windscreen. Mk 2 in front of the intercooler on the left hand side as stood looking at the front of the vehicle). Remove the vacuum pipe and place a tight fitting ball bearing or bolt into the pipe (if bearing fitted reconnect pipe, if bolt fitted secure out of the way) and take vehicle for a good hard drive. If fault has been cured leave EGR valve disconnected.
 
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#4 ·
This is an excellent list of stuff which is exactly what is needed (IMHO) for MEGers to diagnose the fualts themselves or be able to talk to specialists with a bit of knowledge.

Moderators: Can valuable info like this be saved in a locked area and only modified when any improvements/new suggestions become available?

Thanks a lot dieselspecialist!
 
#5 ·
some good ones in there, also one worth adding for the 1.8 boys with the delphi/cav filter primer assembly

uneven idle, which smooths out when the primer is depressed.
later turns into a non start or fuel leak from the split diaphram within the primer.

Can be fixed as a temp repair with an old tyre innertube ;)
 
#7 ·
There is some good advice here. I have always been an advocate of clear sections of pipe in the fuel feeds to the pump (Some Peugeots have them as standard) as air bubbles in the fuel are the enemy of the diesel engine.
 
#10 ·
Problem

· Car lacks power
· Sometimes revs up without actuation of accelerator pedal
· Increase in fuel consumption

Possible cause

· Split boost diaphragm

Diagnosis

· Remove tapered pipe from boost box on the side of the fuel pump (front as you look at it facing the radiator) and check for presence of diesel fuel
dieselspecialist, my is drinking a lot of fuel. Especially in town. 9-10l/100km to say at least. But it doesnt seem to lack power.

By chance after reading your post, I went an check the hose that connects the pump to the turbo (I guess). From the pump it has a short rubber hose and after that it is metallic line. I found the damn rubber hose cracked and immediatelly fixed it. No diesle fuel was present there.

Is this situation included in the quoted message above. I mean, can I expect any improvement in the mileage or power?
:thanks:
 
#11 ·
ok, updates. I drove the car this morning. I did not see any improvements in the dynamics. It's all the same. But that's not unusual. The car had the FLVR sensor "broken" and still accelerated pretty fast.

Should I expect now any improvements in the fuel consumption. I'll try to post some pictures of the tricky hose this night.
 
#16 ·
........If fault has been cured leave EGR valve disconnected.
Forgive me my ignorance, but I've had nothing but problems with the EGR valve on my BMW (Mondie's OK though!). What is it, and what does it do? I only ask this as dieselspecialist's advice above recomends leaving it dis-connected - if this will not ham the engine, I wish I'd known about it £1500 worth of garage bills ago !!!!

JDS
 
#17 ·
EGR allows some inert (exhaust) gas back into inlet manifold to reduce emissions of oxides of Nitrogen (NOx)

This reduces peak combustion temperatures and so prevents Nitrogen (normally inert) combining with Oxygen in combustion chamber.

EGR valve disconnected will increase NOx emissions but generally (IMHO) failure of system is quite common and can lead to all sorts of performance problems?

In my case EGR has been disconnected for years BUT it's a MkI with no electronics to speak of.

With electronics there may be some complications if ECU finds the valve is not working (but I don't know about that)
 
#18 ·
Dieselspecialist: My family has had, and still has, 1.8 Tdi powered Fords for some time. Three Escorts and a Mondeo have all been fitted with the same engine type. One of these, an Escort on a "P" plate, drives fine when it's warm but it is very noisy when it first starts - a serious "diesel clatter". None of the others have done this to anything like the same extent. Why might this be, please. The cam belt was replaced by a Ford dealer and I was assured that it was fitted correctly with respect to the injection timing.
 
#19 ·
Good info above,

Slightly confused about mixed symptoms, so I will descirbe mine. Its a TDC1 130, two and half years old, 102,500 miles. Economy has been excellent (45mpg to 52mpg), but has dropped to 39 in the last 3 fills over the last two weeks (first time ever its been that low). Saturday night started making a whooshing noise coming from behind stereo in centre console, but only when turbo working under acceleration. Lots of smoke too in following headlights. Power loss is getting worse.

Booked in for a service next Friday. I thought it sounded like a burst hose to the turbo, but theres no sign of that.

Any help would be very much appreciated. I can't afford any faffing about next Friday, want to get it sorted quick.

Thouaweek. :(
 
#20 ·
Hi regarding Diesel mondeo TD Faults i have a 1.8 TD Endura engine 96 Mk2 mondeo and it has had several things replaced and yet still no one seems to know whats causing this syptom....

Right from Cold which is at least 12 hours without running the engine,it drives absolutely fine and accelerates nicely......Once warmed up around 5 minutes it begins to have a change of life it loses power,it pulls back when accelerating and as you accelerate it sort of sits there without much change WORSE if attempting a hill...and its like im pulling a heavy load as the engine makes a vibrating sound like the Bigends are gone..

I assumed the turbo was at fault so replaced with a second hand one,and NO change atall,,,,,took to garage they suggested doesnt sound like turbo OR bigends as it wouldnt Idle well and would do the same when COLD engine.

so i changed the Fuel Filter,disconected the wastegate actuator to eliminate this opening to rule out loss of turbo...The only thing mentioned is the MAF Mass airflow sensor,,,,strange thing is if this is disconected it doesnt change the engine tone,and drives just the same???? This i found strange,have yet to replace this but dont see how this could cause this sort of problem...But what else could i suppose...IM New to the forum but will appreciate any advise..Will post back on this if anything changes...
 
#22 ·
Hi Dieselspecialist,
I have a 2.0 tddi and have today changed the fuel filter and syphoned the tank, in the belief that there was water in the tank. (how wrong i was).
The car runs fine on tickover but as soon as it gets warm starts to sound as though it is missing on one cylinder.
When i put my foot on the gas it coughs out white smoke from the exhaust and then eventually cuts out.
i've noticed that if i keep my foot on 2000 rpm the rev counter swings up and down, thats when the car sounds like a bag of spanners.
I would be grateful for some advice. thanks..........
 
#23 ·
Bobdog

Just a thought, could the rattling noise from your engine be heavy diesel knock? usually caused my excess fuel.
Do you get alot of smoke/soot from the exhaust?
Have you changed the fuel filter INCLUDING all the seals (some people leave the top one which lets over time goes hard and lets in air).

I have been told that the MAF does very little, it just controls the timing of the EGR valve.
 
#24 ·
Hi

I've been experiencing similar problems to your Mondeo, including:- drastic lack of performance both on the flat and going up hills, iratic idling, cutting out at traffic lights, accelerating away then pulling back.

The car's fitted with a CAV ROTO diesel injection system; I changed the ROTO-FILTER and blew out the fuel line back to the tank but this made no diference at all.

But then I had a thought, I hadn't inspected the banjo union that fixes the fuel pipe to the fuel filter housing, so I undid the banjo bolt and (low & behold) found a mess of brown slime within the annular internal ring of the banjo union which continued down the tube of the fitting. After clearing out the union I took the car for a test run and it made an 80% improvement, so I looked a little further. I un-crimped the priming pump of the ROTO-Filter and found brown slime within the two neoprene disc valves which was rendering the non-return action of them useless (the fuel was just shuttling back and forth) and wasn't apearing at the injection pump and therefore no performance.

I've re-asembled the filter housing and (hey presto) works absolutley fine.

The slime (I think) is a bacterial goo caused by the disolved water in the diesel fuel and, what with the hot weather we've been experiencing recently has caused an explosion in micro-bacterial action. The banjo union (and the neoprene disc valves) is pre-filter and therefore un-protected, I've now installed an in-line filter so that I don't have to go through all this again (I don't think I'll be able to re-open the ROTO filter priming pump housing any more without it breaking the tabs).

Fantastic job.

I hope this will be of benefit to others in a similar predicament. :D
 
#25 ·
Thankyou for this thread, it was very helpful. My TDCI 130 (5sp) was giving very little power at low revs with great clouds of smoke on accellerator demand followed by reasonable performance. Fuel economy had dropped markedly too. After the garage replaced the faulty MAF sensor which fixed the low rpm power delivery, with the help of your list I was able to figure out that the EGR was duff. The excess soot had clogged it up and it was unable to form a gas-tight seal. Got it cleaned gas tight, disconnected it to keep it that way, and it's running very nicely indeed now. :thankyousign:
 
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