ITP, I presume ...?

[andymc]

Ah, I think I'll have the injectors checked all the same. I'd rather nip things in the bud! Plus I'd been thinking of doing so anyway due to an intermittent noise I've been hearing at low-ish revs, which hasn't disappeared since replacing a worn-out gearbox mount. Not quite sure how to describe it other than to say there's no vibration associated with it, but it could be an injector or the UBP or something else entirely ...

[HarryM1BYT]

Originally Posted by andymc

Even if it turns out that the fault is solely due to injectors and not the ITP, I'm happy enough to have ordered both the pumps anyway as I like to have spares to hand in case of a breakdown. It was quite inconvenient when the ITP failed on another of my cars late last year and I had to put off the repair until the after the pump was delivered, which took a few days.

The ITP doesn't make much noise when running, especially when well covered with fuel. It can be very difficult to hear and only runs for 30 seconds after switch on.

Each injector has a leakback port, it is a matter of checking the volume leaking back from each with bits of tube into glass jars over a short time. Too great a leakage and not enough fuel will be injected into the cylinders, when trying to start up. Once started, the leak becomes less of a problem. Easystart can be used squirted into the intake, to overcome that initial leakage and get the car to start, but it shouldn't be used as a permanent fix.

Injector cleaner might help.

[Mickyboy]

As pointed out already a in tank pump is not easy to hear even if you remove the filler cap and put your ear over the filler cap whilst somebody turns it on it is however easier to remove the seat squab lower base and undo the 10mil bolts over the inspection cover then turn it on and put your ear there you should hear it much clearer that way,

The other thing to remember is that if the car is only running on the under bonnet pump it will put a heavy strain on it, and it may fail shortly after intank pump has been found to be the culprit,

I do a lot of injector testing and one of the symptoms that has become more apparent is smoke on start-up on cold mornings, you should also remember that it’s not just about leak back it’s also spray patterns that need to be correct, to maintain good cylinder balance.

A good two pump system should produce 3.6 bar onwards a single pump system should produce just around 4bar
Mick

[COLVERT]

As for the leak back test if you should want to try it.

Mike Noc has posted some pics of a rig you could use for this test.

I think it can be found in the ---How-To---section of the forum.---

[Mike Noc]

Here you go John.

https://the75andztclub.co.uk/forum/s...d.php?t=223386

[HarryM1BYT]

Originally Posted by Mike Noc

Here you go John.

https://the75andztclub.co.uk/forum/s...d.php?t=223386

Does the engine being hot or cold make any difference to the result, I wonder?

[rustymotor]

Hi, when I was preparing my CDTI for holiday last year, I changed the under bonnet pump for a DMGRS one and kept the original for spare. The UBP became really noisy after 1500 miles, this made me think the in tank pump was failing so kept the car topped up with fuel all the time. Getting back from Spain I tried to hear the ITP but couldn't, removed the seat bolster and used a screwdriver as stethoscope and sure enough it was purring away.

[Mike Noc]

Originally Posted by HarryM1BYT

Does the engine being hot or cold make any difference to the result, I wonder?

A very good question Harry. Also the temperature of the fuel itself may make a difference.

Maybe when things warm up weather wise I'll carry out a series of tests.

[COLVERT]

Originally Posted by HarryM1BYT

Does the engine being hot or cold make any difference to the result, I wonder?

Possibly not Harry thinking about it.

The fuel gets compressed so much ( zillions of psi's ) it must be near self ignition point as it arrives at the injectors.---

[andymc]

Update on this - the mechanic hadn't time to do a full leakback test, but he hooked up the diagnostics and found no issue at all logged, which includes the injectors. He helped me pull out the rear seat and listened for the ITP, but we heard nothing at all when turning on the electrics other than a faint gurgling which would have been caused by the UBP sucking some fuel from the tank - no hum, whine or other noise that could have been the ITP operating. So I'll go ahead with replacing that one & probably the UBP too.

While we had the bonnet open, he pointed out that one of the air intake pipes looks rather swollen & it does feel a bit soft, so it's probably ready to split before much longer and I'd rather replace before that happens rather than after. It comes out of the intercooler on the passenger side of the car and then goes up & back in towards the engine. Can anyone please tell me the proper name for it & where I'm likely to be able to get one - is it worth considering 2nd hand or should I just go for a new one?