Articles about Diesel Air / Fuel Leaks

1. Land Rover Repair -> Freelander TD4 hard cold starts
2. GM-Diesel Discussion -> GRRRRRRRR. Starting problems.
3. Tracking down an Air Leak
   

As always the way, I've come across a great little GEM that pretty much has explained and summarised all what I was trying to capture here in my blog:

DIESEL: TROUBLESHOOTING

Hope you enjoy its information as I have.

Diesel Engine Diagnostic Tips PDF

Guys,

Just come across a very handy PDF cheat sheet describing Diesel Engine Diagnostic tips. Download PDF here.

Glow Plug Information

This information was sourced from - "Winter Starting Tips" article and even though it related to VW diesels the information is fairly similar to all .

Two types of glow plug circuits were used on early and late model vehicles.

1. The slow glow system was installed on early production vehicles;
2. The fast glow on late production vehicles.

Always refer to the relay number for proper identification.

An incorrect match of fast glow relay and slow glow plug will result in premature failure of glow plug and/or relay.

To quick check the system, check the amount of current that is flowing to all glow plugs. A good specification to remember is fast glow plugs pull 12 amps each and slow glow plugs pull 9 amps each.

Listed below are some guidelines to refer to when checking fast glow plug systems.

• 48 amps - all glow plugs are operating correctly.
• 36 amps - one glow plug is defective.
• 24 amps - two glow plugs are defective.
• 12 amps - three glow plugs are defective.
• 0 amp - all glow plugs are defective.

For slow glow systems use the following amp rating to test:

• 36 amps - all glow plugs are operating correctly.
• 27 amps - one glow plug is defective.
• 18 amps - two glow plugs are defective.
• 9 amps - three glow plugs are defective.
• 0 amp - all glow plugs are defective.

The above specifications are applicable to four-cylinder applications. If you have more than four glow plugs, just add 12 amps for each fast glow plug and 9 amps for each additional slow glow plug.

NOTE: Depending on outside temperature, you may experience a surge of current up to 140 amps.

Engine Starts easy when cold but stalls after a short period.

1. Air Leak in Fuel Line / System

Diesels are very temperamental when air enters the fuel system.

Need to discuss / expand:

a. Fuel Hoses from fuel tank into Fuel Fitler and from Fuel Filter to Diesel Pump.
b. Sender and Return fuel hoses at the fuel tank end and how air leak can occur there.
c. Diesel Pump Return line/hose
d. Fuel Spill Over Pipe (small pipe interconnecting Injector spill rail back into the injector pump).
e. Bleeder screw on fuel filter / primer not sealing
f. Fuel filter not sealed onto primer
g. Fuel filter water sensor not sealed or the drain screw not sealing
h. Fuel Primer itself can be a source of air leaks via the hand pump.
i. Fuel Pickup pipe corroded within the tank can allow air leak
j . Fuel Pickup Filter and by pass can be blocked / dirty.

See my previous post "Air leak in Fuel Line / System".

2. Injector Pump

The injector pump has several seals that can and will perish over the lifetime of a diesel engine. However alot of recent failures with diesel engines has been caused by the reduction of sulphur in diesel down to 500 ppm and based on articles that I've read, it is being considered by the fuel / oil companies to reduce it further down to 50ppm. This is were its a little grey for me in that I believe that once you have the seals replaced the seals will be fine on 500 ppm, the failure is caused by the change in fuel mix environment where seals have been conditioned to the higher sulphur levels, but when the sulphur was reduce (less lubrication) it cause them to fail.


My understanding after reading articles is that when the pump seals perish, even though the fuel with in the pump is under a fair amount of pressure, you may not get any tell tale signs of diesel leaking from the pump. So if you inspect the diesel pump and can see a diesel leaking (or if the seals are truely gone - pissing) out of the pump then chances are this could be your source of an air leak within the fuel system.

There is one more seal issue that should be noted here and that is the BIG seal where the pump drive gear bolt together to the engine) that can allow diesel to leak internally into sump / engine block and allow oil to leak into the pump, allow oil to be burn upon a cold start up after the engine has been allowed to stop / lay for a while. Obvious signs to look for is if your oil level increases significantly and or you start find oil within the fuel filter and possibly injectors, you may need to cut open your old fuel filter and check it that way.


3. Possible Heating / Glow Plug Issue

With modern Diesels engine I've read about how they can with reasonable performance start with compression even at low temperatures. So don't overlook them as a potential source of the rough idle at start up. Remember that glow plugs are used to help start the engine but also to help initial running until the engine gets to a normal operating temperature or the max glow plug module time out.

Need to Expand on the following:

a. one or more glow plugs faulty or no longer effective

b. glow plug relay stuffed, hence preventing power to the glow plugs

c. Engine Sensors (i.e. temperature sender) may be stuffed or faulty causing the Glow Plug control module to prematurely shut off. Also the wiring between the sensors and the Glow Plug Module / Control.

d. Glow Plug Module / control itself could be faulty (i.e. capacitor controlling the timing circuit are a known issue on the Pajero's).

e. Depending on your Glow Plug system you may have two Glow plug Relays such as that in the Pajero 2.5ltr has a 12v for initial heating and star then a 6v relay for initial running.

f. Poor wiring / electrical connectivity between relay and glow plugs.

g. Busrail / bar in poor condition hence not providing glow plug with current to heat up.

h. Wrong glow plugs for the vehicle.

Engine Starts easy when cold but run lumpy for short period then runs fine.

1. Air leak in fuel Line / System

This is a possibility, but since it does not stall, the leak or amount of air in the fuel system was small and engine is able to cope albeit very lump.

Please read the following "Air in Fuel Line / System" for more details from my previous post.


2. Glow Plug System Faulty

If one of the glow plugs if faulty or the power supply to glow plugs is faulty then this could cause one or more of the cylinders to run cold and cause the engien to run lumpy until the cylinder reaches operating temperature / condition.

Please read the following "Glow Plug System Faulty" for more details from my previous post.

Engine takes a fair bit of cranking to Start when Cold, but eventually starts.

1. Fuel Supply

With this particular cold start issue, a possibility could be related to the diesel fuel waxing up during cold temperatures caused by the fuel not containing winter mix / additives, or its does and its even more colder than the winter mix is designed/produced for.

If your symptoms is not occurring frequently and only during very cold conditions, then this could be a possible cause. The remedy is to ensure that when you're entering cooler / cold conditions such as ski fields / alpine regions that you have filled your fuel tank up with winter mix.

Another scenario is outback Australia were its get fairly hot during the day, but bloody freezing at night, in this case none of the fuel outlets will have winter mix, and so to rememdy this you go to a local auto store or fuel station and pick up fuel additive ensure that you add to the tank when you expect these conditions are about to occur.

-=-=-=-=-=-=-=

A subject to discuss and expand on is when you don't have access to winter mix / fuel additive is the use of a small amount unleaded petrol to help prevent waxing. I've read a few articles and they state pros and cons of doing this. Please until I've fully understood it myself do your own research and if anything lock it away as an option if absoloutely needed when you are unable to obtain winter mix / additive and there is a change you're about to encounter cold condition and you fell you diesel will wax.

-=-=-=-=-=-=-=

2. Low Compression

As expected with diesel engines the fuel is ignited under the correct compression ratio and heat. If one or all of your cylinders are starting to experience low compression, then this could make it harder to start a cold engine.

I found the following article - "Compression Test" useful for detailing Compression Tests on both Petrol and Diesel engines.

3. Air in Fuel Line / System


There are a few causes that may cause air to enter the fuel system.

a. Fuel Hoses - There are a few to check / replace

1. Input and Output fuel hoses of the Fuel Filter / Primer (8mm I/D)
   
2. Return Fuel Hose (6mm I/D) from Injector Pump to pipe back to the tank.
3. Sender (8mm I/D) and Return Fuel (6mm I/D) Hoses on the Tank End.
4. Spill Over / Fuel Leakage Pipe (small pipe from middle injectors back to injector pump).

These hoses can perish over time. This could lead to air entering the system and you may not even be able to find the crack. It only cost about few bob per meter of fuel hose worth the investment and piece of mind nothing that you've done them.

The other part to this one is the fuel hose clamps, make sure they are secure / tight proper hose clamps (smooth inner bore) not standard jubilee clips that will tear / pierce into the host



b. Clogged Fuel Filters

Obvouiosly this can affect performance of a diesel engine, and eventually hinder even stop a diesel engine. Make sure you replace fuel at the specified km's / interval.

c. Water in the Fuel / Fuel Filter Water catchment full

Water in the fuel system can affect the performance of a diesel engine, cause it to stall and if large enough quantities kill the engine (ie water in via the air intake).

The fuel filter water catchment chamber that collects water from the fuel system may be full. Normally fuel filters have a water sensor that screws into the buttom of ther filter which will alert the drive when the chamber is full or nearing full. But this should normal not occur between regular fuel filter replacements unless you have encounter a very dirty source of diesel or water has contaminated the fuel tank some how.


d. Fuel Water Sensor leak

The water sensor that screws into the buttom of the fuel filter should always have the o-ring / replace before being screwed into the filter. This ensure that leak are prevented. However leaks can still occur if the plug is not total and securely screwed into the fuel or worse and shamelishly the water drain plug is not tightly shut off /screwed on.

e. Fuel Filter / Primer leak

The fuel filter seal onto the primer may not be air tight. Each time you replace your fuel filter you should make sure you add a little oil / fuel on the new seal of the fuel filter before screwing it back on to ensure a good air tight seal.

The Primer pump itself can be a source of air leak.


f. Fuel Pickup pipe corroded within the tank can allow air leak

z

g. Fuel Pickup Filter and by pass can be blocked / dirty.

z


4. Engine Block / Sump oil Heating Unit Failure

Depending on were you live and the weather condition you experience, vehicle come with or have aftermarket block heaters fits which plug into mains to heat the engine sub oil and block to enable diesel engines to start easier / possible. I've have no experience with these units but can appreciate that they can and do break down. And when the breakdown your engine maybe next to impossible to start without the vehicle being kept in a warm area.

5. Glow Plug System Faulty

The function of the glow plug is to heat the cylinder area to help diesel ignite inconjuction with the correct compression ratio. It usally comes down to glow plugs for a diesel engine having trouble starting cold. There are a few components within the Glow Plug System that could fail causing the failure to correctly heat the cylinders during a cold start.

a. Faultly Glow Plugs - Short / Open circuit

When testing Glow plugs, I've read there are two typical faults that occur with the glow plug itself (Open / Short Circuits).

You can test glow plugs in situ, however only for Open Circuits. To test glow plugs in situ you will need to remove the interconnecting powe bus bar / rails connecting each glow plug else if at least one of them working the test would always work. Once you have the bus bars off, if you use a test pen / lamp and connect one end to the positive terminal and then touch the tip of each glow plug, if it lights up then the circuit is complete and the glow is allow power through it.

However if there is a short with in the glow plug then the previous test will work, but because there is now a shorter path for the current to travel the plug will not heat up.

The best test is take them out and visually inspect them but applying power. To save me a bit of time, the following articles are brilliant source of information about glow plugs and how to test them. Even though its targeting VW vehicles, majority of the concepts are shared amongst all diesel engines:

VW Diesel Glow Plugs
VW Diesel / Glow Plug System
VW Diesel Glow Plug Control Circuit

One important bit of advice from these article I got and that is you should always test NEW Glow Plugs, just because they are new doesn't mean they are not faulty.

Here are some You Tube videos, the first one is current proedure for testing glow plug, the second video, well lets just say I wouldn'y advise it, but its cool to look at :).

Video 1 - VW Rabbit pick-up diesel glow plug test
Video 2 - Glow plug test

b. Incorrect Glow Plugs for the engine

I've read of instances where people have incorrectly put glow plugs for the Turbo Diesel Intercooler engine into a Natural Aspirated Engine causing it to be a very hard start. The other scenario is putting 12v Glow plugs into 6v systems meaning the glow plugs don't heat correctly.

Another common fault I've read about is that of "false ecomony" were people have experienced the hassles of purchasing cheaper brand of glow plugs but only to find out they are fairly short lived and start playing up.

Please consult the catelogs and look for the glow plugs for your vehicle and engine type (ie Turbo, Intercooled). Also stick with the tried and tested brands of glow plugs.

c. Poor or no power supply to Glow Plugs

There are a couple of places along the glow plug power supply line that could cause problems.

First test is to perform is to see if you are getting power to the glow plugs. This is fairly straight forward in that using a multimeter on DC volts mode you put the negative probe to the negative terminal or a good ground source on the chasis. Then put the positive probe on the 1st glow plug. Have someone else turn on the ignition to warm the glow plugs and you should see 6v or 12v depending on your vehicle for about at least 10 sec (even after the glow plug dash board indicator has went off). Repeat this for each glow plug.

Even if you are meauring correct voltage there could still be an issue with the power supply in regards to poor connections or faulty wiring which prevent the correct amount of current to be supplied to the glow plugs. Remember that glow plugs on average draw upwards of 36/48 amps depending on number of cylinders and voltage 6v or 12v - see here for more.

Second test to perform is to trace / check the wiring to the glow plugs, look for poor connections from battern to glow plug relay and then onto the first glow plug. Make sure now of the connections have corrusion and are tightly secured and making a good connection. With the pajero and many other diesel egines, the power is wired to the first glow plug and then distributed to the other glow plugs via a power bus rail (several metal strips interconnecting each glow plug. Each of these connections need to be checked and cleaned securely bolted to the glow plugs.

If this has resolved your issue, the next test to check for faulty glow plugs see previous section.


d. Malfunctioning Glow plug Control Module / Relay

If even after checking the glow plug power supply (fuse, wiring, power bus bar/rial) and assuming you have a good battery then it starting to indicated that your glow plug control module and or relay is stuffed.

The easiest way to test this is power / jump the glow plugs manually using a length 6mm wire with appropriate connection to bolt to the first glow plug and run to the positive battery. If you clip it on to the positive and wait say 10 seconds and then attempt to start the car.

If this resolves your troubles and the engine starts, then you will need to look at replacing the glow plug control module / relay or if that looks like its going to be too costly, I've read articles on how people have installed a proper manual power circuit to power the glow plug manully from the vehicle's dashboard. Please read this article - "Pajero Glow Up"


6. Injector Pump

z

7. Injectors

z

Types of Diesel Cold Start Issues

After researching diesel cold start issues for diesel engines I've come to understand the following common set of symptoms encountered during a cold start:

1. Engine takes a fair bit of cranking to Start when Cold, but eventually starts.

2. Engine Starts easy when cold but run lumpy for short period then runs fine.

3. Engine Starts easy when cold but stalls after a short period.

4. If your are unlucky you could experience combination if not all of the above scenarios :(


But depending on your cold start symptoms will depend on which tests you could perform to narrow it down or correct the issue.

I'm sure there are a few more symptons that exist, and if you have these symptons let me know, and more preferably provide solutions on how you diagnosed your symptons to fix the cold start issue.

Description of My Diesel Cold Start Issue

Paddy (Thats my Pajeros Name) developed its intermitting cold start issue around Feburary 2008. Its inital issue was that it would start pefectly but after about 10 - 20 sec the engine would run "lumpy" like one or more of its cylinders was not getting fuel or heated enough, and there was moderate amount of smoke coming out the exhaust. With a little increase of the engine RPM to about 1500-2000 the lumpiness would work itself clear and the engine would run fine. Once the car had past its first start of the morning, ever other engine start was perfect and no sign of the lumpiness.

But the intermitting issue became more persistant (as anything would do if it does not get fixed) and eventually even upping the RPMs to 2000-2500 would not help and the engine would simply stall and there was a shit load of smoke coming out of the exhaust during the lumpiness. The restart would take a fair bit of cranking, once started a little lumpy then all was good.

I jumped onto the Pajero 4WD Club of Victoria Forum and started the following thread "NJ TDi 2.8 Strange Start issue" This thread started expanding my knowledge of diesel cold start issues alot. After some very help advice, I followed some advice regarding air in the fuel system and I bled the system the cold start issue disappeared. And so let my guard down and thought I had won.... but only after about 3-4 weeks, it came back with avengence.

During my initial investigation when trying to work out what was happening I decided to do the following test to see what would happen. I started the engine and raced round to the fuel filter / primer and just as the engine started to run lumpy I pumped the primer a few pumps and the engine ran smooth. Then starting lumpy again so I repeated this process 6-7 times and then the engine ran fine. And as usual all other engine starts during the day, the engine started and ran without any hiccups.

This same initial test was the only process that would stop the Pajero Diesel enigne stalling during cold start so it meant I still had an issue with my fuel system. This started me down my path of researching and attempting to gain a better understanding of diesel fuel systems.

Please bear with me as I start doing a brain dump of what I've learnt and think I've understood. Then I'll start to expand on each sympton and tests and details as I have time. Over time with with your feedback, hopefully we'll have a nice little knowledge repository top cope with "Diesel Cold Start Issues".

Pajero Cold Start Issue Introduction

G'day All,

Well if you are here you are most likely researching for solutions / symptoms regarding the nortorious Diesel Engine Cold Start Issue. As you will know, this issue is not just specific to Pajero's. Actually all diesel motors will experience cold start issues at one time or another.

Earlier research on a number of forums indicate that it is a notorious Injection Pump Seal issue that the Pajero 2.8 Diesel experience. But there are a fair number of other causes documented as well. So Instead of me jumping to the conclusion that its the seal, the purpose of this blog is to document my research and knowledge I've gained while diagnosing my Pajero's Diesel Cold Start problem.

If you, while on your search for anwsers, find any information you think should be added here to help others please let me know :)


The Legal Stuff:

Before we get started or too far into all the fun, this information is by no means the word of a Qualified Mechanic. I'm bar far a Qualified Mechanic, I'm just a simple bloke who is not afraid to get his hands dirty and tinker with electrical / mechanical objects as long as I have a reasonable manual, guide / HOWTO.

So please make sure that you understand that anything said in this blog, by me or anyone, that you accept that myself and anyone else that posts information on this blog do not take responsibily or liable for any damage that this information may cause to yourself or engine / vehicle.