high pressure fuel regulator

I've got the high pressure fuel regulator off with a view to replacing the o rings and gasket. On inspection there doesn't seem to be much wrong with the existing rings and gasket. No deformity, anyway. But there was a bit of gunk. Not much, but I'm guessing its the last place it should be.

Is it ok to blast it with some carb cleaner?

Do the regulators fail in ways other than the O rings and gasket deforming?

I also noticed that there was a groove for a larger O ring on the regulator, and that this was missing. I assume it was not critical, since it has been working ok for years, but I wondered if it would be a smart move to put one on. I don't know if it is missing on purpose and won't align properly if I put one on.


Any replies gratefully received.


On a secondary note, when I took off the air intake to gain access I noticed that the new air intake temperature sensor I had put on was very oily. The old one wasn't when I removed it (few weeks ago now). I wondered if the excess oil around the sensor was an indication of a different problem that may be causing the hot start issues (Won't start when engine hot. The reason for removing the regulator in the first place).

MGT said:

I've got the high pressure fuel regulator off with a view to replacing the o rings and gasket. On inspection there doesn't seem to be much wrong with the existing rings and gasket. No deformity, anyway. But there was a bit of gunk. Not much, but I'm guessing its the last place it should be.

Is it ok to blast it with some carb cleaner?

Do the regulators fail in ways other than the O rings and gasket deforming?

I also noticed that there was a groove for a larger O ring on the regulator, and that this was missing. I assume it was not critical, since it has been working ok for years, but I wondered if it would be a smart move to put one on. I don't know if it is missing on purpose and won't align properly if I put one on.


Any replies gratefully received.


On a secondary note, when I took off the air intake to gain access I noticed that the new air intake temperature sensor I had put on was very oily. The old one wasn't when I removed it (few weeks ago now). I wondered if the excess oil around the sensor was an indication of a different problem that may be causing the hot start issues (Won't start when engine hot. The reason for removing the regulator in the first place).

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Hi there, yes the solenoids can fail. You’ll have running issues that are clear if that’s the case.

Yea gunk in the hp pump won’t help anything, cleaning is good idea. Brake or intake and carb should be fine, just don’t fill the pump up with it lol.

Yea there is usually two o rings. I suspect one peeled off when you removed the valve/solenoid. Use mirror to look inside you might find it in pump.

Yea intake usually oily. Mine always is.

Hard start when hot is often sensor related. Often cam sensor but can be others or wiring related. It’s easy to do a basic check in a cam sensor with a multimeter and some back probes.

Sensor testing;

Essentially they are 3 pin sensors usually, power/ground/signal. If you remove the sensor from cam cover and then plug it back into the engine harness and put ign on. Now connect meter probes to ground and signal of sensor via back probes (don’t pierce or mangle your wiring). When the sensor reading face is presented with metal and then not you’ll see the voltage change from 0-12 (or whatever you current batt voltage is). If the sensor doesn’t react to metal when hot and readings don’t change the sensor is duff. Often a failing cam sensor works when cold again so if it fails the test hot Chuck it in the fridge or freezer for half an hour. Upon installing the sensor again if it now works and starts again you’ve now doubly confirmed it’s a bad sensor.

Thanks Ross. The cam sensor is newish but it was a cheap part. I will test it if the new o rings on the regulator don't fix it. I wasn't talking about the small o rings that go on the pin but down near the gasket position on the broader section. I've seen a couple of regulator replacements that have the groove filled by an o ring. I'll take another look at them. Solenoid is off or on, isn't it? Ie, if its broken then the valve will either be open or closed. If it's closed presumably pressure builds until there is a breach in the fuel rail, if it's open then presumably pressure can't build to fire the injectors. SO I figure if it starts and runs on idle the valve must be working.

MGT said:

Thanks Ross. The cam sensor is newish but it was a cheap part. I will test it if the new o rings on the regulator don't fix it. I wasn't talking about the small o rings that go on the pin but down near the gasket position on the broader section. I've seen a couple of regulator replacements that have the groove filled by an o ring. I'll take another look at them. Solenoid is off or on, isn't it? Ie, if its broken then the valve will either be open or closed. If it's closed presumably pressure builds until there is a breach in the fuel rail, if it's open then presumably pressure can't build to fire the injectors. SO I figure if it starts and runs on idle the valve must be working.

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If it was a cheap part it may have failed already.
The manual shows one big and one small o ring on the solenoid. It’s pwm controlled so can be operated from 0-100%. This system is slightly different than I thought, the solenoid controls the high pressure return. When it is de energised the valve is open and no pressure is built in the rail. When the solenoid has full time power (100% pwm) the valve is fully closed and the system can create maximum pressure. The ecu controls how much the valve is closed using pwm this in turn controls rail pressure. The pumps maximum pressure is up to 1,300 bar.

Ross Tait said:

If it was a cheap part it may have failed already.
The manual shows one big and one small o ring on the solenoid. It’s pwm controlled so can be operated from 0-100%. This system is slightly different than I thought, the solenoid controls the high pressure return. When it is de energised the valve is open and no pressure is built in the rail. When the solenoid has full time power (100% pwm) the valve is fully closed and the system can create maximum pressure. The ecu controls how much the valve is closed using pwm this in turn controls rail pressure. The pumps maximum pressure is up to 1,300 bar.

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Thanks. So presumably the valve is linked into readings from the high pressure sensor on the common rail. I will look up symptoms for that failure too. Thanks for your help. I'm going to bolt it all back together and see if it works.

MGT said:

Thanks. So presumably the valve is linked into readings from the high pressure sensor on the common rail. I will look up symptoms for that failure too. Thanks for your help. I'm going to bolt it all back together and see if it works.

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Hi, yeah the ecu monitors rail pressure via the rail sensor (analogue sensor with 0-5v output). The required rail pressures according to rave manual is 200 bar min to start engine, 300 bar idle and 1,300 bar system max. There is a common problem for the rail sensor plug/wiring for which I believe there’s an updated part. Although I expect you’d see sensor problems on live data. If the sensor goes bad you can have starting and running problems. I believe if this sensor fails the car likely won’t start to prevent damage.

Ross Tait said:

Hi, yeah the ecu monitors rail pressure via the rail sensor (analogue sensor with 0-5v output). The required rail pressures according to rave manual is 200 bar min to start engine, 300 bar idle and 1,300 bar system max. There is a common problem for the rail sensor plug/wiring for which I believe there’s an updated part. Although I expect you’d see sensor problems on live data. If the sensor goes bad you can have starting and running problems. I believe if this sensor fails the car likely won’t start to prevent damage.

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Thanks. It's all back together now and the difference on the rev counter is phenomenal. I'd forgotten it could rev like that, so the regulator seals must have been degrading for a while I think. Thanks to Nudge 68 and others for the original tip (another thread) and your good self. I have one remaining query if you are able to oblige about the return hoses on the injectors The one on the end of number one injector blew off and poured diesel everywhere. I figured an airlock maybe so reattached it and it seemed to anchor. But one of the link hoses was spraying as well (not enough pressure to blow it off though, and it's only a short link between two injectors.

I figure maybe the hoses had degraded over the years but because the pressure was lower it hadn't caused a problem - ie, the increased pressure in the system is showing up the weakness. If it's that then I can just replace them. However, if it is something else I'd be grateful for any advice.

MGT said:

Thanks. It's all back together now and the difference on the rev counter is phenomenal. I'd forgotten it could rev like that, so the regulator seals must have been degrading for a while I think. Thanks to Nudge 68 and others for the original tip (another thread) and your good self. I have one remaining query if you are able to oblige about the return hoses on the injectors The one on the end of number one injector blew off and poured diesel everywhere. I figured an airlock maybe so reattached it and it seemed to anchor. But one of the link hoses was spraying as well (not enough pressure to blow it off though, and it's only a short link between two injectors.

I figure maybe the hoses had degraded over the years but because the pressure was lower it hadn't caused a problem - ie, the increased pressure in the system is showing up the weakness. If it's that then I can just replace them. However, if it is something else I'd be grateful for any advice.

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No problem glad it’s going well.
It’s a bit strange the return hoses coming off or leaking. I guess if the hoses were degraded enough they might not be a tight fit anymore and could be susceptible to coming off with pressure. I would inspect them and test how easily they pull/come off (not running).
Although I’m also suspicious there could be too much pressure in the return line for some reason forcing them off. A blockage or other fault could cause that.
Maybe start with the hose inspection.

Ross Tait said:

No problem glad it’s going well.
It’s a bit strange the return hoses coming off or leaking. I guess if the hoses were degraded enough they might not be a tight fit anymore and could be susceptible to coming off with pressure. I would inspect them and test how easily they pull/come off (not running).
Although I’m also suspicious there could be too much pressure in the return line for some reason forcing them off. A blockage or other fault could cause that.
Maybe start with the hose inspection.

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The one that blew off number one injector when I fired the engine up was well anchored (and not leaking) after I put it back on, which made me think of an air lock finding the weakest point in the system to vent. Didn't happen when I replaced the injectors though. I must admit I am worried about excessive pressure in the system too. I didn't know the return hoses carried fuel at pressure. The other hose that is leaking now is sprinkling diesel like a small fountain. I suppose there is another possibility - the regulator not working so there is no way to take pressure out of the system. But then the high pressure fuel sensor ought to pick that up and shut everything off. I would have thought. I'll take your advice and check the lines tomorrow. Thanks.

MGT said:

The one that blew off number one injector when I fired the engine up was well anchored (and not leaking) after I put it back on, which made me think of an air lock finding the weakest point in the system to vent. Didn't happen when I replaced the injectors though. I must admit I am worried about excessive pressure in the system too. I didn't know the return hoses carried fuel at pressure. The other hose that is leaking now is sprinkling diesel like a small fountain. I suppose there is another possibility - the regulator not working so there is no way to take pressure out of the system. But then the high pressure fuel sensor ought to pick that up and shut everything off. I would have thought. I'll take your advice and check the lines tomorrow. Thanks.

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Yeah an airlock shouldn’t blow it off as everything moves one way in the system. The return flow is usually quite fast but doesn’t build pressure so to say. None of the injector return hoses are clamped so not expecting pressure there. I’d you can observe live data you could check the rail pressure.
Well yeah the pressure regulator was open too much that would cause excess return pressure.
Check the return hoses first for cracks and loose fitment first. Then maybe move on to live data of needs be.

Ross Tait said:

Yeah an airlock shouldn’t blow it off as everything moves one way in the system. The return flow is usually quite fast but doesn’t build pressure so to say. None of the injector return hoses are clamped so not expecting pressure there. I’d you can observe live data you could check the rail pressure.
Well yeah the pressure regulator was open too much that would cause excess return pressure.
Check the return hoses first for cracks and loose fitment first. Then maybe move on to live data of needs be.

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Thanks for your help, Ross, I will check the hoses tomorrow.

regarding the return hose connectors :
'tis not a bad idea to get rid of the factory plastic one's .. as they can fail.,
and replace them with brass fittings ..
e.g. https://www.ebay.co.uk/itm/183770305020
.

hd3 said:

regarding the return hose connectors :
'tis not a bad idea to get rid of the factory plastic one's .. as they can fail.,
and replace them with brass fittings ..
e.g. https://www.ebay.co.uk/itm/183770305020
.

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That's great, thanks. I had no idea they existed. Assuming I can fix this issue I will get a set in. Good price too.

Ross Tait said:

Yeah an airlock shouldn’t blow it off as everything moves one way in the system. The return flow is usually quite fast but doesn’t build pressure so to say. None of the injector return hoses are clamped so not expecting pressure there. I’d you can observe live data you could check the rail pressure.
Well yeah the pressure regulator was open too much that would cause excess return pressure.
Check the return hoses first for cracks and loose fitment first. Then maybe move on to live data of needs be.

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Meant to say thanks for the tip - I had trapped the return hose when I put the manifold back on. Replaced that and it's fine. I also trapped and flattened the harness to the high pressure fuel sensor at the same time. So lesson earned not to be in a hurry.

MGT said:

Meant to say thanks for the tip - I had trapped the return hose when I put the manifold back on. Replaced that and it's fine. I also trapped and flattened the harness to the high pressure fuel sensor at the same time. So lesson earned not to be in a hurry.

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No worries. It’s easy for these things to happen, especially if it isn’t something your used to doing. Don’t worry too much about flattening cables a bit but do check no insulation is/was broken, as you don’t want any copper wire exposed anywhere.