One step forward and two steps back

[Binny]

After nearly twenty five years of being off the road I now have my 2.5 pi running albeit on axle stands BUT there are a couple of issues.

The first problem is that the engine runs unevenly with a very ‘fluffy’ exhaust note and the odd back fire when the throttle is opened. I think this is down to low fuel pressure which is only 85 psi. Spark plugs 1,2,5 & 6 are very light in colour indicating a lean mixture whilst 3 & 4 are more sooty but that could be due to weeping injectors. The fuel pump has been completely rebuilt and adjusting the PRV seems to make no difference. Is this likely to be a faulty pump or PRV? It’s worth mentioning that all the injection equipment is off a car that last ran 35 years ago although all the seals have been replaced and everything thoroughly cleaned.

The second problem is that when running there is a trickle of engine oil appearing from the cylinder head to block joint just below the spark plugs. There is no cross contamination between engine oil and coolant. Is this an indication that the head gasket needs replacing?

Thanks for any advice.

[Alec]

Hello Binny,

While the fuel pressure is low, it's not drastic unless it falls further when the throttle is opened?
A check on the injection timing is the first step. With number six injector line removed at the metering unit and the check valve to which it is attached is then removed leaving the rotor in view. With the engine at number one cylinder firing you should see a hole in the rotor at the number six port. As long as this hole is coming from the top that's OK, it should not be disappearing to the bottom.
A copy of the Lucas Service manual is available from the register Regalia section and at £5 is very good value. Alternatively the Register's Service Notes is also useful and has a section on the injection system. Both are invaluable as is a reasonble quality vacuum gauge.
If you remove the injector clamps, and with the engine running, remove an injector one by one and point it to the inlet manifold port to observe the injector operation, ther should be a nice cone shaped mist from each one. You can have a dribbly injector but that will often clear by gently pulling the end of the injector with some small pliers, which usually will dislodge whtever is trapped there.

Plug colour reading really needs to be done on load rather than just at idle.

I presume that a new fuel filter element was fitted and that all fuel connections to the pump are tight and leak free. A poor connection can let air into the pump affecting pressure. The pressure relief valve can be dismantled, it's quite a simple device and should be spotless inside. Any foreign matter that prevents the valve from seating properly could be the problem, but if screwing the plunger in does not improve pressure it probably is a pump that is down on output. As I said air leak on the suction is one possibility, another is how many volts is actually being supplied to the pump on load. A simple check is to run a length of cable of a reasonable cross section direct from the battery to the pump and see if the output pressure improves. Do not forget the earth connection to the body, ensure that is sound.

The oil leak is a bit of a nuisance and if torquing the head doesn't cure it then a new gasket would be the answer. However, I would run the car on the road when you can and see how it develops.

good luck,

Alec

[Binny]

Alec, thank you for that very comprehensive and helpful reply.

Happily I can confirm that I now have fuel pressure of just over 105 psi and the PRV responds to adjustment. The problem was the mechanical part of the pump which I swapped for another that I had along with an old spare PRV.

That said you’ve slightly confused me with regard to timing the metering unit. The manual I have always used is the Autobooks OWM784 which is dedicated to all the Mk 2 models. On page 45, Fig.2a :6 shows the range of permitted port positions for No.1 cylinder firing in A with the rotor hole disappearing at the bottom of the port whilst B shows the incorrect port positions with the rotor hole coming from the top. I’ve always timed my system based on A. I seem to remember that the similar port positions diagram in the Haynes manual is slightly incorrect, isn’t it engines after MG75001E (mine’s well before that) that should be timed with the rotor hole just appearing from the top ?

With regard to the oil leak I shall retorque the head nuts to see if that cures things although there is now a very small pool of coolant under the rear of the engine which doesn’t seem to be any of the hoses or metal pipe, all of which are new. If re torquing doesn’t work then I think it’s a case of ‘off with his head’ as the rocker gear is completely black which might indicate worn guides so I might replace all the valves and springs

[Alec]

Hello Binny,

it is well documented that many manuals show an incorrect rotor port position, opposite of what it should be.
What you have is the incorrect position, and the Register Servic Notes actually states that the engine will run but be 'fluffy' which is what prompted my suggestion.
I don't think it matters too much whether it is an early or late engine. Essentially, with the engine at number one firing, the number six cylinder will just be commencing it's induction stroke so timing at the start of that makes sense. With it at the bottom you will be injecting earlier, i.e. during the exhaust stroke.

Well done on the pump front. The Lucas service manual says the injectors should operate as low as fifty psi, but a poor pump usually results in too low a flow which means a poor response from the engine.

Road test nearing?

Alec

[Binny]

Thanks once more for your response Alec.

It’s frustrating that the various manuals give conflicting and inaccurate information - even the Lucas manual is spectacularly vague on metering unit timing.

What you say makes perfect sense although when I refitted the distributor drive, pedestal and metering unit drive pinion everything was aligned exactly as shown in the manuals. When the metering unit was fitted the scribed marks on the rotor and body were in alignment and it fitted perfectly without any movement of the rotor, consequently I now have the hole in the rotor just disappearing when the crank is at TDC with No.1 cylinder firing.

If I am to alter the timing so that the rotor hole is just appearing at TDC then something else will be out of alignment, however, it’s certainly worth trying.

I’ll report back.

[Alec]

Hello Binny,

there is no prescribed position for the metering unit timing. Yes there is the alignment beteen pedestal and metering unit but that is rarely disturbed.
My method is to remove the number six line and the number six non return valve to which the line attaches.
Remove the distributor and put to one side.
Unscrew the pedestal from the block.
I use a three eights drive extension bar and use it to hold down the distributror drive shaft (So it doesn't come up with the pedestal and come out of engagement with the camshaft possibly altering that timing.) as I pull the metering unit pedestal upward and disengagae it from the distributor drive shaft gear.
The next step is a bit of guess work and takes me a couple, sometimes more tries. I turn the gear in the pedestal relative to what I observed before I removed it.

Assuming your position now with the hole disappearing, I would turn the pedestal drive gear, say one eighth of a turn anti clockwise looking from the the drive end, i.e. so the rotor turns upward. Refit the pedestal and check, you will see the rotor turn as it engages with the distributor drive shaft. If required repeat with another adjustment until the hole is appearing from the top, even a near full hole is acceptable.

At least once done it does not need re doing very often.

Alec

[Binny]

Thanks Alec.

I’ve just whipped the metering unit off and I was maybe over confident of things being properly aligned. I know there are different methods of removing it but I just undid the three set screws which hold it to the pedestal. Upon checking with a mirror the slot in the drive pinion was not as vertical as I’d thought.

Anyway I turned the pinion so that now I have almost a full hole appearing in the port at TDC and it seems to be slightly less ‘fluffy’. I might see if I can refine that further but suspect that if I turn the pinion any more that there’ll be no rotor hole showing at all.

Also I think it might be beneficial to remove the head and replace the valves, sleeves and springs as there’s quite a bit of exhaust like smoke coming from the breather on the rocker cover.

[Alec]

Hello Binny,

different methods.
I never disconnect the flange with the three set screws.
I remove the two nuts holding the pedestal and metering unit as one to the block.

I would not start playing around further without some road miles, engines really need load and as yours has not run for along time, let it settle down on the road and you'll have a better perspective, in my view.

Alec

[Binny]

Hi Alec,

Unfortunately I’m some way off being able to put some road miles on the car. I’ve spent the last few months laying on the garage floor welding the bodywork and now I’m converting it to power steering and installing an anti roll bar. Once that’s done then I want to have a running and moving vehicle so that I can start the filling, profiling and spraying of the body work on the driveway.

[Alec]

Hello Binny,

I understand.
I know how much work is involved and how long it takes. At least you have a running engine, so I suggest you put that to the back of your mind and progress on it once the car is mobile?

Alec