Recent travels

[David2021]

I took the 12 Tourer down to Hampshire from the Midlands last weekend. It was on duty as the wedding car for my granddaughter's wedding in Steep Marsh. (A bit of a contradiction in terms that name!) I used the A 3400 through the Cotswolds to Oxford and the A34.to Winchester then over the A272 to Petersfield. Apart from the dual carriageway A34 the roads had not changed much since when the car was young! Apart from much more traffic and proliferated Road signs! The weather was pretty hot, but the car ran coolly...60-70C on the gauge...almost needed a radiator muff! Inside the car with the tonneau fitted vents open and sidescreens down, it was quite warm, but ok. A bit of heat insulation above the exhaust pipe might help...but then in winter (no heater) the heat will be good! Oil pressure (rebuilt water/oil gauge recently fitted) had been erratic compared to the "original",but this run appeared to have got it to settle down: 60psi at 60mph looked good to me. I'm using a 20/50 traditional multigrade, changed every 1000 miles. Oil level about1/4" down and the lubricator reservoir level had dropped satisfactorily. A very pleasant round trip of about 300miles...I haven't checked the fuel consumption, probably not as good as I would like. The only "problem" I had was that after a heavy braking application the engine did not want to pick up smoothly, it felt as if the fuel level in the carburettor had surged, no wild ticking from the pumps suggesting vapourisation. Once it cleared the car again ran perfectly.☺ Any ideas out there?

[SHyslop]

Dear David,

I saw your post a little while ago but was away on holiday. Having returned, I see you haven't had a reply but hope the following may be of some interest and possibly use. I'll tell the story first then tie it in with the specifics in your question. Firstly, I should say that I have a 1947 12 saloon which is an export model (Jersey - not as far travelled as might have been!) with an SU electric pump fitted from new on the bulkhead in the same way to your tourer along with the Solex carburettor. I am interested that you say "pumps" and I wonder if you have dual pumps the way some of the MG TDs had but that's an aside.

Anyway, I also have a few six cylinder Rovers as well, all but one having been fitted with electric fuel pumps. Of the electric pumped cars, one has a D3 SU carb and two have Solexes. On coming to my ownership, one car had an electric SU pump under the bonnet (a puller pump) and two had the MGB type pump under the back seat - a "pusher" pump.

The two cars with the pusher pumps ran excellently from the word go. The car with the front mounted pump was mysterious. It would start ok, run all right but uphill lost all go and had little accelerative powers. I tried everything I could think of - ignition, different jets, different carburettor innards (float, needle valve) but with the same disappointing results.

Now, I should also say I have a 2 1/2 litre Riley RMB which was also equipped from new with a front mounted puller SU pump. This feeds twin SUs and in over 20 years has never had a lack of go in the 60 - 70+ mph range whereas the Rover with 1901cc was running out of go at 45 mph.

This had lead me to think that the puller SU pump should have adequate capacity for the Rover, being mounted in a similar location and with a similar configuration of supply and carburettor. However, I was able one day to stop when the car was going poorly and check how much petrol was in the float chamber and the answer was - not a lot.

As I had a spare new MGB type pump in the boot of the MGB, I reworked the Rover's system to have the pump at the rear and the problem was instantly solved. I should also say that I had tried several spare new SU puller pumps plus a modern type pump of another make before relocating the pump - none of which made any difference.

I should say that in telling this story a month ago to another Rover P2 owner who was also telling me of difficulties with a flat spot/loss of performance, he was sceptical as to the reliability of what I was telling him. However, going from no solution with everything else to a solution with this course of action leads to the conclusion that this was where the problem lay with this car. I won't take up extra space here by going into why I reckon the puller pump was failing despite all the external signs being good. Having said all that, I don't think that's the most likely thing going on with your car but it may give you food for thought of something to consider if what comes next doesn't yield any improvement.

In your description, you say that the problems you had occurred after heavy braking. That means that the engine was idling and you went from the pilot jet to the main jet when accelerating, the pilot jet only operating at idling speed and the main jet inactive due to a lack of depression in the choke. The lack of go could either be caused by too much air or too little petrol. If too little petrol, it might be an idea to check that all four spraying holes and the air holes in the emulsion tube are clear. I have been finding that, even with E5 petrol, once the spirit has evaporated, it can leave behind deposits which block the jets in Zenith and Solex carburettors. I wouldn't think this could happen quickly enough in the time you were braking but a check over that everything is as clear as it can be would be half an hour well spent as something may be partly blocked. If that doesn't help, it might then be worth considering the speed with which the carburettor is being replenished with fuel given that the bowl is rather small. I can't say I have had exactly that same problem with my 12 but it has taken me some time to think it is running as "right" as the cars with an SU and a mechanical pump.

Finally, and probably not terribly relevantly, I just remembered a problem I had years ago and I remember intermittently to check. If one of these cars has a metal or armoured covered oil pressure pipe and also has screw on brass spade spark plug terminals, or a no. 4 (or 6) spark plug terminal with defective insulation, it is possible for the terminal and the pipe to come into intermittent contact through braking and accelerating thereby shorting out that cylinder intermittently. It can be awkward to diagnose if a bakelite lead and distributor cover is fitted.

I'm not entirely convinced that the above contains "the answer" but possibly something may be a starting point.

[David2021]

Thank you for that considered and useful reply
I confess to not knowing if my SU pump pushed or pulled! All I was aware of was the it appeared to work ok. Even in very hot weather tt seemed to work pretty well, it does have an insulated heat shield...it was installed on the cocit side of the bulkhead when I got the car ,this I considered not a good thing.
I will check out the carburettor though. I have an ultrasonic cleaner that really does sort out the nooks and crannies. Something that may be relevant (or not!) Is that I still get the odd backfire on the overrun which I think is caused by air being sucked in via the manifold. I have to check all the gaskets & joints for air leaks. The car does seem to have low cylinder compressions (but very even over the 4 cylinders)
I am happy that the ignition circuits are good.and the timing and distributor are correct..
I have a suitable new SU carburettor (which would probably need re jetting, but as the car (apart fron this little hiccough) seems to be generally ok on the original set up I am not minded to try it yet
I will see what cleanine and sorting out air leaks does
D

[TonyG]

Hi David,

A thought re your recent problem; at the time of your heavy braking, how much petrol was in the tank? Is it possible that the fuel surged forward enough to allow air to be sucked through the pick up? Just thinking that the regular pick up, as opposed to the reserve pick up, is a fair bit shorter. If you had half a tank or more this is unlikely of course but would explain why the problem cleared and hasn’t returned.
My SU pump is mounted on the bulkhead and ‘pulls’ the fuel. This was the recommended set up for this pump when I fitted it and has never been a problem. However, mine is feeding two carbs so there is twice the reservoir capacity to manage any shortfall in flow, if that is your problem.
A small point is that you will need to change the needle, not the jet, if you decide to use the SU. Burlen Services can help with the correct one.

Tony.

[David2021]

Belated reply Tony!
I am "having a go" at the car tomorrow and will tighten up all the flanges and look at the carb interior...
My reserve pipe/unit is not fitted...the car had it closed off when I got it & I have acquired one, but not fitted it yet...we will check to see if the solenoid works tomorrow, but I think the car was over half full when it faltered.
David

[TonyG]

Hi David,

Hopefully you have explored a few options around your running issue and resolved the problem. If not, another thought related to smooth fuel delivery is; do you have an in-line fuel filter installed and does the tank pick up pipe still have the fine gauze filter on the end? My thinking is that the harsh braking may have stirred up sediment in the bottom of the tank, which either clogged the gauze filter or got through to the carb. An in line filter should have protected the carb but that doesn’t prevent the pick up pipe getting blocked a bit. Also, if the reserve has been disabled it is likely that the longer reserve pipe is being used at all times to make use of the tank capacity. However, this increases the risk of picking up sediment. My Tourer has suffered from this exact problem, resolved each time by removing the pick up pipe to clean the gauze and by draining the tank of fuel and separating the sediment before reusing in the lawn mower. An annoying issue as I had the tank blast cleaned to remove rust and identify any weaknesses, thereby guarding against this problem. Typically, the ‘sediment’ in my tank is actually blasting grit that has remained despite the tank having been well flushed!

Anyway, as I said, just a thought. These things are usually simple fixes but determining what to fix is the hard bit.

Tony.

[David2021]

Got a bit sidetracked! Managed to open up the replacement reserve pick up, the solenoid leads were crumbly and shorting as the solenoid windings filthy! The mechanical bits were full of crud, but look ok...they are going in the ultrasonic cleaner. Then solder on new leads and see if it works! The current fuel pick up certainly has good gauze anD the ta K was cleaneD out and treated with sealant, no sign of serious debris in the carb. I still have to find out what I did to make the ignition light stay on...nothing obvious loose or detached. Two steps forward, one back☺

[David2021]

At the NEC on the RSR stand I asked the question & it was pointed out that the engine to chassis earth strap might be missing... sure enough no sign of a strap! Connected the engine to the chassis by using a jump cable.....ALL IS GOOD Possibly the old worn engine mountings were acting as an earth, and had been for years!
Cable ordered...there is a redundant 1/4" hole in the top of the chassis on the offside...nothing obvious on the nearside...so I will run the new cable from that hole to one of the bellhousing bolts...unless anyone knows better!

[HAD501]

Hello David
I think this is the "official" position of the earthing strap as shown in the lower left of the photo. The chassis end of the strap is under one of the bolts securing the engine mount cradle to the chassis. Obviously from the electrical point of view you can put the strap in any convenient place.
DaveM

[David2021]

I will have a look and see if I have one there!! If I have, it's not working