TR6PI ('74) no fuel cylinder 2

[Agile]

Dear Forum,

I having a question on the PI system of my TR6PI '74 (Bosch pump). The engine has been running great but last week started to misfire. I noted no pulsation on cyl 2 and 5. Cleaning #5 with compressed air and it started spraying/pulsing again. However, #2 does not seem to get any fuel from the metering unit.

Question: with the injector disconnected, should some fuel eventually flow out of the (nylon) feed-line from the MU with the engine running (on the remaining 5 cylinders ...)?

Several other posts suggest replacing the banjo-bolts on the MU for cylinders 2 and 5. I believe the non-return valve is part of the banjo bolt. Correct? Could the no-fuel problem be due to defective non-return valve?

[peejay4A]

Yes, that would be my suspicion.

[Agile]

Thanks Pete!

Staring at a TR6PI is not going to fix it. So, I reconnected the #2 injector again, started it and ... after a while it started to produce a nice "spray". Once inserted again, misfire gone. Is it right that no fuel will flow from a feed-line with no injector connected? Anyhow, looking in my logbook, I had a problem with a blocked injector before, on ... #5, so will definitively order new banjo-bolts (and non-return valves?) and install these (requires MU removal - right?).

Tip for newbies (like me): I also used a screwdriver as 'listening-aid' to listen to the injectors. Place it on the top of the injector and 'listen' via the handle (or use a more sophisticated device). You can 'hear' very well those not working well.Together with the pulsation of the feed-lines should give you a good indication of which injector is not OK. BTW funny to note that they all sound somewhat different.

W ytze

[Mike Collins]

Before you remove the banjo bolts mark the banjo itself so the same face is refitted against the MU body. I found out the hard way that they may not be symmetrical, continuous injection if wrongly fitted.

Yes MU has to come off for access.

 

Mike.

[Agile]

Thanks Mike!

Is my understanding correct that a Banjo Bolt (part# 518630) actually contains the non-return valve for cyl 2 and 5? Where the other 4 have the non-return valve in a part referred to as the 'union' (known as LU60600197, set of 4 with a 5th one for the inlet (?) with one the suppliers)?

Would you recommend replacing all of them or start with the Banjo Bolt ones as only these require removing the MU?

Thanks, W ytze.

[Mike Collins]

Yes, non return valve is part of the banjo bolt, exchange bolts are not very expensive. It makes sense to me to change both as removing the MU is a pain.

 

Mike.

[astontr6]

Before taking out the non return valves, are you certain that the O Ring in No 2 injector is not leaking and causing drain down and letting in air in No 2 injector fuel line? This usually happens when the car is left for any length of time, with out the engine running.

 

An old Lucas/CAV. method of priming the fuel lines, is as follows:

 

With the Injector removed, hold fuel-line near vertical, using a plunger-type oil can filled with petrol, hold the nozzle against the fitting, squirt petrol into the injector fitting until line is full. Then screw injector back on to the fitting, this ensures that when the non-return valve opens that it is not pumping against air and any trapped air is now near the injector. This method ensures that you are not having to crank the engine for the next 10 to 15 minutes and saves a lot of frustration.

 

Bruce.

[John390]

The 'O' rings on number 2 and 5 banjo fittings break up and block the injectors with bits of rubber. Just replace the 'O' rings and blow out the pipes and injectors. That should cure it .

 

Cheers John

Edited September 16, 2016 by John390

[Agile]

Hi Mike, Bruce, john and Neil,

Thanks for the feedback.

Yes, the problem occured when I used the TR6PI after a relative longer break (few months). It started after some cranking and - as usual I would say - initially ran on a few cylinders only to pick up on all 6 within a minute or two. That same day, back from the office, it kept on misfiring on 2 and 5. Blowing the injectors solved this. I noted no fuel spill when removing #2. After cleaning, starting remains 'as usual': initial not picking up on all 6.

Based on the feedback - thanks again - I will next get new O-rings for 2 and 5, remove the UM, blow out all (including the non return valves) and see what happens! If the 2/5 banjos/non return valves look bad, I'll replace those as well. Got feedback that these are quite robust and typically do not fail (other then due to debris).

I will let the forum know in due time what the result is.

W ytze

[astontr6]

Agile,

 

Have you replaced no 2 injector with a known good one? This would be my first course of action. Yes the O rings on non-return valves 2 & 5 do break up! I had this problem 3 years ago but also had injector O ring poppet valve failure as well on some of the injectors. In the end I replaced all the injectors, as KMI had changed their injector spec. of their O rings so that they would with stand 15% ethanol petrol formulae. Another problem that I have suffered was, the white locking sleeve inside the injector body/ injector poppet valve coming un done. This gives the same effect as injector O ring failure, i.e. will not hold pressure

 

Bruce.

[Agile]

Hi Bruce,

Yes, 1st thing was to swap injectors. this confirmed earlier conclusion (based on no pulsation on respective injector feeds and no/poor 'ticking' sound with 'screwdriver' test): an injector problem. Once cleaned out with compressed air, injectors worked OK, no more misfires. Not immediately starting on all 6 cylinders after some time not driving remained. This is not an urgent/huge issue. Nevertheless, next I will remove the MU (a first in my case) and ensure no debris in the non-return valves and replace the o-rings on the banjo bolts for 2 and 5. I have just ordered these o-rings.

I did check the injector white locking sleeves and their O-rings, they were OK. I had replaced them some time ago when installing new injectors.

Remark: I had disconnected the fuel line from the pump at the metering unit and noted a small filter inserted in the union. This filter was clean, no debris. So, I think the (aging) fuel tank is not the culprit for any debris (or my fuel filter does a great job). I will replace the fuel filter as well and physically opening the old one will give some further hints regarding the fuel tank state.

W ytze

[Denis]

When reassembling to avoid fuel leaks (bad news near the Dizzy!) I grease the main 'O' ring between the Pedestal and the M/U, and I grease the plastic Dog-Drive to help it stay in place in the drive slot !

 

Another tip, I ground down the Ring of a Ring Spanner to nip the Banjo bolts up when the M/U is bolted back on.

 

Good luck, horrid job, but all part of the fun of ownership!

[Agile]

looking forward to the job :-) For now waiting for the parts to come in (as well as some extra spare time).

Denis and all, thanks for the tips. I intend to follow the Brown Book (section 19.35.07) as main guidance and have also ordered a new MU-to-pedestal sealing o-ring (part 149486). I noted that no torque is specified for the 3 MU fixation bolts.

W ytze

[Agile]

Just a brief update:

"yes, the rubber rings in the banjo's of #2 and #5 disintegrate and will cause injector malfunctions"...

 

I can't seem to find the torque to use when fastening the banjo bolts. Would someone have know that?

In some other post I found 150 ft-lbs, if I correctly convert that, it would be 200 Nm which seems like (way) too much.

Edited September 22, 2016 by Agile

[astontr6]

Agile,

 

Looking at your picture, I know that problem well! When you fit new O rings, make sure that you blow out the injector feed tubes as bits can lie up in the tubes, with the injectors removed. Also if your injectors are old, the injector poppet valve O rings can suffer from the same fate? As did mine! The non return valves are just nipped up using a ring spanner or socket!

 

Remember my tip to back fill the injector tubes with petrol, before fitting the injectors! Saves all that cranking!

 

Bruce.

[MortenHoyseth]

Agile,
careful when tighthening the banjo bolts to the MU body. 200Nm is FAR to much. I don't recall exactly (believe I found it in the workshop manual) . The MU body is alu, and it's very easy to damage the threads by over-tighthening. I've ruined one MU body due to this. You could always contact e.g. Prestige Injection and I'm sure Malcolm will sort it out for you if needed.

[k_raven_smith]

ONLY NIP THEM !!

[Guest ntc]

ONLY NIP THEM !!

+1

[stuart]

ONLY NIP THEM !!

+2 otherwise thats how the "O" rings get chewed and the threads get stripped.

Stuart.

[Agile]

Not too tight - got it. But not being a native speaker:

verb (used with object), nipped, nipping.

1. to squeeze or compress tightly between two surfaces or points; pinch; bite.

So, how to quantify " nip it"? My guess: "as one would normally do"

[jamesStag]

Hi Agile, ah yes English is a confusing language at times. The dictionary def may not be that useful here. In terms of mechanics to 'nip up' is essentially to lightly tighten. Another way I'd describe it is imagine if you were tightening two nuts against each other on a thread. You can run the nuts together by hand, then to secure them it just needs a small part turn with a spanner, Perhaps 1/16th of a turn, if that? You should not need to use much effort at all.

Hope this helps...

J.

[Agile]

Hi James,

Thanks, very useful! "Nip up +1"!

W.

[jamesStag]

Hi Agile, glad to help....

Cheers, J.

[Agile]

Just to feedback on progress.

Installed the new rubber O-rings on the banjo bolts and cleaned out both #2 and #5 banjo's, fuel lines and injectors with compressed air. I noted the orientation of the banjos to ensure replacing them in the same direction. However, I could not see any notable difference, to me they seem symmetrical, yet better safe than sorry. Since you now have easy access, I checked the cold start enrichment lever gap. I replaced the non-return valves banjo bolts while at it, but the existing one ones indeed seem to function quite OK as Neil predicted. I tightened the banjo bolts by 'nipping them' :-) tnx James! I replaced the O-ring between the MU and pedestal as well A tip earlier this tread (thanks Denis): add some grease to the red drive dog, this will make it stick in the MU while you put it in place. Prior to MU removal, I had set the engine in #1 TDC-Fire position as per the Brown Book. In that position the slot in the MU is exactly horizontal, which makes installing easier as the drive dog will not fall out 'by default'. Following Bruce' tip I filled the fuel lines and the injectors with some fuel using a syringe before connecting the injectors to their feed lines again. The engine started with minor cranking and ran on all 6 immediately. Similar pulsation on all feed lines. Test drive in the near future. I did not tighten the 3 MU bolts with the prescribed torque, it is a somewhat of a challenge to get access to the 3 bolts with a normal ring spanner, getting a (small) torque wrench in position: something for diehards. I forgot to order the O-ring between the fuel inlet union and the MU body, so this is for the next time. Take care that you do not loose the small fuel filter in that inlet (or find it on the workbench when you are all done).

Thanks to the forum for their valuable contribution and guidance!!

W ytze

Edited September 27, 2016 by Agile

[astontr6]

Agile,

 

I am glad you got it fixed!

 

Bruce.