Amazon: Engine not running properly

[JDW3696]

Hello. Does anyone have any idea what could be up with my B18 engine? Its a B18a but has twin su's.
The fuel tank was full of rust and gunk, it was replaced with another clean one and fuel pipe was replaced. Thats the fuel issue it had sorted, the mechanic has also said that it is running badly as it is running on just cylinders one and three on idle and not all of them through the rev range. Carb float chambers were full of muck so they are being looked at and cleaned out and I'm still waiting to hear the results of a compression test which I'll hopefully find out about tomorrow. Fingers crossed its something simple. Anybody have any ideas. I really hope its not something up with the pistons or the piston rings and praying the compression test comes back okay.
Thanks
Joe

[Rustinmotion]

What do the plugs look like? Sooty black? Oily black? Light brown or white?
If the compression test comes back ok I would check
Correct firing order
Leaks in intake manifold
points and condenser
Plugs, can you move the problem by moving plugs
Plug leads , can you move the problem by moving leads

[Burdekin]

As recommended before; Do a full tune up; ignition and fuel and a full service. If you’re not up to it take it to a classic car mechanic, forget about modern mechanics they often have no clue with old cars. Any half decent classic car mechanic will be able to check through the ignition/timing, fuel, tappets adjustment etc which will probably sort your problems.

[Burdekin]

This always splits opinion but personally I’d fit a 123 electronic distributor and possibly a new coil as well. The old ignition system will work perfectly well if all in good condition but I like the simplicity of the 123 dizzy. Change all the spark plug leads for new decent ones and all new spark plugs.

[Derek UK]

Note that fitting twin carbs to a stock B18a gives very little in the way of benefits. You need to upgrade the cam as a first step to make the twins work. CR may still be low but with modern, poor, fuel that isn't such a bad thing. If your B18A originally had a downdraught Zenith it can get a boost by fitting the later single Stromberg with its related manifold. This is combined with the twin down pipe exhaust. Yes you will need the matching front exhaust pipe but overall a worthwhile upgrade. One which will give you better all round running than with the added twin carbs. Selling the twin SU's should pay for the Stromberg conversion. Don't look down on a Stromberg B18A, it works very well, especially on a daily driver. Good low down torque and a smooth runner.

[Othen]

Originally Posted by JDW3696

Hello. Does anyone have any idea what could be up with my B18 engine? Its a B18a but has twin su's.
The fuel tank was full of rust and gunk, it was replaced with another clean one and fuel pipe was replaced. Thats the fuel issue it had sorted, the mechanic has also said that it is running badly as it is running on just cylinders one and three on idle and not all of them through the rev range. Carb float chambers were full of muck so they are being looked at and cleaned out and I'm still waiting to hear the results of a compression test which I'll hopefully find out about tomorrow. Fingers crossed its something simple. Anybody have any ideas. I really hope its not something up with the pistons or the piston rings and praying the compression test comes back okay.
Thanks
Joe

The B18 is a pretty simple unit, so you just have to work through the issues methodically. I always think it is best to do the diagnosis oneself rather than entrust it to a garage, but no matter.

I compression test is a really good place to start - there isn't much point fiddling around with the fuel and ignition systems if it isn't mechanically sound. If the rings, bores, valves and head are all proven okay by the test then the issue has to be either fuel or ignition.

I'm guessing the motor has the twin SU manifold from a B18D or similar, so as cylinders 1 and 3 are working okay it seems unlikely to be the fuel system - the carburettors feed cylinders 1/2 and 3/4 respectively. It still might need tinkering with but that can't be the reason for cylinders 2 and 4 not working.

That leaves the ignition system. I wouldn't spend too much on new parts just yet, leave that until you have the standard setup running properly. Assuming it is standard, then that is a really simple system. It is rather unlikely the coil is affecting only cylinders 2 and 4, so we can probably discount that at the moment (which is convenient if you have an armoured ignition cable). That leaves the points, capacitor, plug leads and plugs. Have a look at the points, see if they are pitted and if not fit them again and make sure they are gapped properly. Check the capacitor by flicking the CB points open and seeing of it gives a big spark. Have a look at the plugs for the usual clues and then clean them. Test the plugs one at a time for a spark, then swap the plug leads (swap 3 with 4 and 1 with 2) to see if any fault moves with the swap. Now check and adjust the ignition timing with a strobe. So far you will have either found an issue or checked everything is working the way it should - so try the motor again to see if cylinders 2 and 4 still aren't working.

The above shouldn't take more than about an hour or so, won't cost anything and should reveal why only 2 cylinders work. If you still have an issue then just carry on being methodical and eliminating one thing at a time.

Good fortune.

Alan

[JDW3696]

Hello. Thank you for your advice so fortunately I have been called this morning with the result.
All the fuel system was full of gunk so its had a new fuel tank and pipe, carbs etc all cleaned out. Compression came back as being good fortunately. It turns out the choke on one carb wasn't connected and the other was stuck on, apparently the jets were well passed it too so it is now running well. The issue now is the battery isn't charging which I am guessing is the new voltage regulator isn't wired properly or is faulty or the dynamo is knackered. Apparently only getting 10v. Thats the next thing to figure out. I am getting closer to driving it though and thankfully the engine wasn't knackered.
Regarding the twin carbs and a different cam apparently the engine was rebuilt so hopefully it has a better cam. I have no way of knowing though. I'm going to try and get in touch with the previous owner. To be honest as long as it is driving well that's all I care about for now.
Thank you for the advice.
Joe

[Othen]

Originally Posted by JDW3696

Hello. Thank you for your advice so fortunately I have been called this morning with the result.
All the fuel system was full of gunk so its had a new fuel tank and pipe, carbs etc all cleaned out. Compression came back as being good fortunately. It turns out the choke on one carb wasn't connected and the other was stuck on, apparently the jets were well passed it too so it is now running well. The issue now is the battery isn't charging which I am guessing is the new voltage regulator isn't wired properly or is faulty or the dynamo is knackered. Apparently only getting 10v. Thats the next thing to figure out. I am getting closer to driving it though and thankfully the engine wasn't knackered.
Regarding the twin carbs and a different cam apparently the engine was rebuilt so hopefully it has a better cam. I have no way of knowing though. I'm going to try and get in touch with the previous owner. To be honest as long as it is driving well that's all I care about for now.
Thank you for the advice.
Joe

Hi Joe,

That is good news about the compression test. It would seem that the garage's previous diagnosis that cylinders 2 and 4 were not working was a complete red herring. It is good that the fuel problem was easy to diagnose, although a garage should have noticed the choke not being connected from the outset. It is good news that it is running well.

If the dynamo isn't working it may be sensible to consider an alternator modification now. It wouldn't really cost any more if the old system needs to be replaced and is a much better long term solution.

I wouldn't worry about camshafts and so on at the moment, just get that B18A/D running properly.

Good fortune.

Alan

[JDW3696]

Thanks Alan. If it is the dynamo then yes I might consider and alternator conversion. I was thinking about doing that in the future. There is a company that do alternators in the guise of a dynamo or ill look into just fitting an alternator.
Joe

[Othen]

Originally Posted by JDW3696

Thanks Alan. If it is the dynamo then yes I might consider and alternator conversion. I was thinking about doing that in the future. There is a company that do alternators in the guise of a dynamo or ill look into just fitting an alternator.
Joe

I'm not sure I'd worry too much about having an alternator disguised as a dynamo; an alternator conversion is a perfectly sensible and acceptable thing to do:



I've just looked on the Brookhouse Volvo site and can see it sells an alternator kit complete for £270, which is a tad cheaper than an exchange dynamo (£282). Unless it is a really easy fix I'd say it wouldn't really be worth trying to repair a dynamo system.

Good fortune,

Alan