PI Constant spray from injector engine not running

[brucer]

I have ongoing problems with the PI system on my TR6. The current fuel system consists of a Bosch pump and a modern diaframe pressure regulator. Earlier this year I found that some of the injectors were leaking, so I replaced them all with a reconditioned set. This appeared to work for a while, but now I can see that at least one of the injectors is spraying continuously even when the engine is not running.

My thought was excessive fuel pressure.

 

Is this a likely explanation, or is there something else I should be looking at?

Thank you in advance for your help

Regards

Bruce

[john.r.davies]

The injectors spray when a pulse of pressure from the M/u artives, and overcomes the tension in the internal spring.    So continuous spray says that the injector needle is stuck open.   Debris in the system?

Hokd the valve WIDE open briefly, by gripping the needle in the finger nails ( never pliers!) In the hope that 'bits' will wash out.

John

[trchris]

Hi Bruce l would suspect the injector isn’t closing properly allowing the fuel pressure to escape l would remove and see if any debris is stopping it closing normal cause sometimes 

Chris

looks like Johns beat me to it 

Edited December 12, 2025 by trchris

[brucer]

Thank you both. I've tried exactly what you suggest, but no change. The spray pattern looks perfect, it's just spraying all the time the pump is running.

I'm suspecting that something has gone wrong with the metering unit, hoping it's not that.

 

Bruce

[Spit_2.5PI]

Bruce, the space between the alloy body and the steel sleeve of the MU is full of petrol at continuous pump pressure. The nose of the outlet connection (which contains the one-way valve) goes through this gap and seals on the sleeve. I wonder if this seal has broken down somehow. Perhaps the outlet connection is no longer tight in the body?

Cheers, Richard

[john.r.davies]

Bruce,

Do you have The Manual?   See: https://www.lucasinjection.com/MANUALS.htm

And Page 3.    The body and  sleeve in the M/u should be so tight that pressure can't get through.  The sleeve rotates to open each port to the injectors and delver a pulse.   If the sleev was so worn that pressure does get through , then it would cause continuous squirting from all injectors.   IMHO, of course.

JOhn

PS The Wheatsheaf Press used to publish a facsimile copy of the original manual.   They are now "Wheatsheaf Print" and I don't know if the Manual is still in print, and they don't have a website, but are at:

Wheatsheaf Print, The Printworks Lacey Green, Wilmslow, SK9 4BQ Directions

Tel: 01625 530530

J.

Edited December 12, 2025 by john.r.davies

[Peter Cobbold]

If the continuous-spraying injector changes after turning the engine over, it suggests to me that the shuttle is allowing fuel to pass to whichever port is open. A worn shuttle could do that. But the engine may still run OK under load, when the shuttle excursion is allowed to increase.  Peter

 

[brucer]

Thanks for those suggestions. I'll go and do some more investigation.

@Richard I'll check and make sure they are tight.

@John I don't have the Lucas Manual, but the website you linked to was very informative.

@Peter I have found that if I can get the engine to run without it getting totally flooded, it does run OK under load but terrible at tickover.

Sounds like I might be in for a new/reconditioned metering unit.

Bruce

[Schnippel]

2 hours ago, brucer said:

Ich habe anhaltende Probleme mit dem Einspritzsystem meines TR6. Das aktuelle Kraftstoffsystem besteht aus einer Bosch-Pumpe und einem modernen Diaframe-Druckregler. Anfang des Jahres stellte ich fest, dass einige Einspritzdüsen undicht waren, also habe ich sie alle durch einen überholten Satz ersetzt. Das schien eine Zeit lang zu funktionieren, aber jetzt sehe ich, dass mindestens eine Einspritzdüse permanent Kraftstoff einspritzt, selbst wenn der Motor nicht läuft.

Ich dachte, es läge an zu hohem Kraftstoffdruck.

 

Ist das eine plausible Erklärung, oder gibt es noch etwas anderes, das ich in Betracht ziehen sollte?

Vielen Dank im Voraus für Ihre Hilfe.

Grüße

Bruce

Hello,

If an injector nozzle is continuously spraying during pre-injection, a banjo seal is defective! Under no circumstances should the machine continue running! The machine can be ruined in a short time; piston seizure is likely. The system pressure of approximately 7.8 bar is reaching the nozzle directly through the defective banjo seal. If this happens unnoticed, it's a catastrophe for the machine. The worst possible fault on a Lucas system.

Best regards,

Ralf

[brucer]

Just had another tinker and things have changed.

The injector that was spraying continuously has now stopped. 2 other injectors are dripping slowly so not sealing properly. 

I'm now wondering if the "Reconditioned" injectors I bought were a waste of time. They did come from K Raven Smith on Ebay. Might go for a new set. even though they are mighty pricey.

@Ralf, thanks for that information.

I think I'll take another look tomorrow, and if it's not spraying continuously, I'll take it for a run up the road.

I will report back tomorrow.

Thank you again for all your help.

Bruce

[Trev Good]

Some reconditioners simply blow compressed air or fuel through an injector, then call it reconditioned. I'm not suggesting the person you bought from did just this, but it happens!

[Steve-B]

Were I you I’d send the injectors to Mike Bilney or Neil Ferguson  for a proper reconditioning. Affordable and quick service to eliminate any doubts. 

Edited December 13, 2025 by Steve-B

[Chris Hale]

Sorry wrong post

Edited December 13, 2025 by Chris Hale

[Chris Hale]

8 hours ago, brucer said:

They did come from K Raven Smith on Ebay.

I have never had a problem with stuff from Neil 

[k_raven_smith]

Regarding the the injectors I reconditioned for you I can assure you I DON'T just blow air through them. As for the leaking this is normal and allowed by Lucas in their workshop manual. The problem is more likely to be the bung seals in the metering being passed there best. Neil Fergusson (k- Raven-Smith)

[Spit_2.5PI]

23 hours ago, john.r.davies said:

And Page 3.    The body and  sleeve in the M/u should be so tight that pressure can't get through.  The sleeve rotates to open each port to the injectors and delver a pulse.   If the sleev was so worn that pressure does get through , then it would cause continuous squirting from all injectors.   IMHO, of course.

I would just take issue with you there John. It's the ROTOR which rotates. The sleeve is fixed within the body of the MU, not least because the nose of each outlet (screwed into the body) seals in the various orifices of said sleeve, fixing the position. My point is that if the seal (an o-ring?) of one of these outlets was faulty, that would give the path for pump-pressure fuel to that ONE injector, whatever the position of the rotor.

Cheers, Richard

[Steve-B]

Hve you checked the injector lines are not loose at the MU? I accidentally did that once for unspectacular intermittent issue. Another thing to check is the rubber rings in the white seals that push into the Intake Manifold, as if those have failed you'll not have a good seal, again learned that the hard way...!

 

[brucer]

On 12/13/2025 at 10:54 AM, k_raven_smith said:

Regarding the the injectors I reconditioned for you I can assure you I DON'T just blow air through them. As for the leaking this is normal and allowed by Lucas in their workshop manual. The problem is more likely to be the bung seals in the metering being passed there best. Neil Fergusson (k- Raven-Smith)

I did attempt to contact you directly, but you never responded to my eBay messages. I'm sure you are a busy man.

I know you are a reputable reconditioner of Lucas fuel injection systems and would never suggest otherwise. My thought process was that maybe someone else was masquerading as you on eBay. I should have come here in the first place. 

Thank you for the information regarding the small leakage.

 

Regards

Bruce

 

Edited December 15, 2025 by brucer

[brucer]

@Steve-B Yes I have checked that.

I did not get a chance to work on this over the weekend. I will update as soon as I can get some time to do some more tinkering.

Thanks again for everyones help.

[Steve-B]

@brucer You might want to consider removing the injectors, injector hoses and MU as a group and sending to Carl at TR Trader. He'll completely recondition, bench test, new Vitron seals, and diaphrams for a reasonable price. Then you'd have the knowledge of that part of the system being up to current spec.

I'm about to send him my spare MU to do just it so I have it ready just in case...

[harrytr5]

We are blessed in having PI specialist and the knowledge they have. Here is another one that I have had great success with.  Martin Giles (Fred Millturn) 07970 935472 in St Neots

who works closely with KMI  ( I knew Ken Mills Injection years ago when in Acton) his grandsons took over when he retired. Martin Giles has updated lots of Pi stuff. Check out his website.

As I say, we are blessed with PI Specialist's  and lucky to have them !

Early days we did not and earlier no factory trained mechanics either on PI.

Merry Christmas

Regards Harry

[brucer]

Thank you, everyone, for your help and a special thank you to Martin Giles (Fred Millturn) for his superb service. My injection system is now sorted with a reconditioned Metering unit and Injector pipes. I think my main problem was that 2 of the injector pipes had failed and were leaking.

Changing the metering unit was a fiddly job, but would be much easier if I hade to do it a second time now I know what tools to use for which bolts.😄.

 

Regards

Bruce

[Steve-B]

👏 Superb news Bruce, and just in time for many a hopefully (!!) dry days now!

[Andy Moltu]

A leaking injector pipe wouldn’t explain continuous spraying from the injector. More likely a failed seal in the metering unit.

Injector fails usually  manifest themselves as dribbling, irregular spray pattern or non injecting. 9 times out of 10 it’s crud/debris in the injector for which the solution is usually blowing through with an airline. The small internal o-rings do fail eventually and are simple enough to replace unless they are of the “crimped tip” variety.