Project 1974 MGB GT - The Mustard (Mit) Mobility Scooter - 6yrs ownership & the end is potentially nigh!

[mrbenn]

I'd cast a suspicious eye towards the condenser while you're at it.

[SiC]

It was running previously on a point assisted unit. This would take most of the stress out of the points and would barely need a condenser. IIRC I modified the unit to put a ~15mA load across the points. Which should just about be enough to keep them clean.

[SiC]

Just nipped up to fetch the battery. Turned ignition on and the pump merrily ran away to reprime the system. Couldn't see any overflow out the bottom. Gave the carbs a tap with a mini claw hammer. Didn't make any difference. 

Pulled plug number 1, it wasn't wet. Hard to tell under the security lights in the car park but it did look a bit on the lean side. 

Tried turning it over but it managed about 2 rotations before the solenoid started clacking. Battery is now on charge, ready to go back to the garage tomorrow morning.

I'm sort of suspecting fuelling issue. Can't imagine stuck floats, as to happen to both carbs together?? As Phil said, the B-series should be capable of running two cylinders - albeit badly. I think I've done it before by putting my hand over a carb to stop any airflow in when tuning them.

Need to make a list of things I've changed and any observations when it failed for the garage. 

[mrbenn]

I had a few issues with the Minor some time ago which were fairly similar to this, turned out to the the low tension wire on the side of the distributor had all but worn through. Wasn't visible until completely removed from the car.

[SiC]

The points assistance unit has a wire straight from the points to the box, without going through the loom. The other connections then connected onto the Coil. I also have a direct connection from the fuse box unfused side to the coil positive. When I disconnected the points assistant unit, I reconnected the old wire from the coil to the distributor. 

I've looked in the points assistant unit and there is no obvious failure to it. However I've not had a chance to power it up on the bench for a proper test. Could well be that has failed and also the loom wire to the distributor is failing. IIRC it was a bit iffy now I come to think about it.

[1970mgb]

Ouch! What a way to start the year.

A B engine is surprisingly drivable on 2 cylinders. Yes, it will feel like you're trying to move a boat every time you accelerate, but it will go and will even get up to decent speeds and hold them(provided you don't have to go up grades). Aside from that, even if one carb packs up and dies completely, remember that the intake manifold has a cross-over pipe between the two inlet ports. That means that even though the front carb MOSTLY feeds the front two and the rear MOSTLY the rear two, all cylinders will still get some.

Dry plugs+presence of a spark tell me that it's most likely not an ignition issue. If it were a weak or improperly timed spark, I'd expect wet plugs.

One of my first tests would be-as suggested above-to spray some ether into the intake and see if it will at least fire on that. It won't run long on that(you might get a few seconds) but if it at least "kicks" a bit you'll know that it's not getting fuel. Absent that, you can even try dribbling a bit of fuel in the carb throat.

That aside too, I've seen/heard of some really weird vacuum leaks that caused a sudden non-running situation. A few months back, one guy on the MG forum had a lifter failure(weird by itself) but when it happened he had a backfire that popped a core plug out the end of the intake manifold. Even without lifter failure, something crazy like that can cause it to not run at all.

[captain_70s]

Dashpots still full? The Doloshite's ran empty (within a few miles on a warm day) as the oil was too thin and the piston jammed at the bottom of it's travel. Unlikely on twin carbs but perhaps worth a quick look.

[SiC]

Freshly charged battery on it. She started right up! Fast idle possibly a bit low but she would sustain running off throttle and a chunk of choke at 800rpm. Bleeding bloody bastard thing.

 

Went through all what happened with the mechanic and I've left it with them to diagnose. Couldn't think of anything obvious off the top of his head. I did suggest a vacuum leak and he said he seen rough running if the manifolds aren't sealing properly after mixture adjustment. But didn't think it would cut out suddenly.

 

One thing I did think of was that both sections of the motorway I cut out on were steep inclines and then low/off throttle downhill. So I suggested the vacuum advance may have got stuck at full. He reckoned it'd still run, just roughly and pinking. Also he said when he did the timing check, the vacuum advance didn't look like it was working. Common thing that he almost always sees on them. I moved the plate by hand earlier, it moved fine and smoothly.

 

 

[Kiltox]

Bloody hell, what an ungrateful bastard this is. Hope the garage can get to the bottom of it. 

[Mr Pastry]

5 minutes ago, SiC said:

Common thing that he almost always sees on them.

TADTS.  When I worked in a garage, our standard knowledgeable response to the customer when faced with a baffling problem was "It's a common fault.  We've come across this before"  ?

[Tamworthbay]

Could it be fuel vaporisation? Long run on incline producing higher than normal underbonnet temperatures, followed by off throttle period where fuel movement is low. Fuel lines just replaced - possibly too close to manifold or other heat source?

[purplebargeken]

Whatever the problem is I hope it is quickly and easily rectified mate. 

[SiC]

Fuel pump.

The carb end was disconnected and it ran for a bit then petered out. Currently has one of those blue Hardi German units on. Apparently gravity isn't enough to fill these carbs, they do need a bit to force them through.

Either the pump or possibly the connections. I suspect pump as it's only pulling 4 amps or so when running. Hardly enough to be too much of a draw on dirty contacts for it to fail on a short run.

Had to be something obvious, there isn't too much that can cause a sudden failure.

[Joey spud]

I'm not saying it isn't the pump but with my ex Rac patrol hat on i wouldn't of said 4 amps is too far off the norm.

As a rough guide at the roadside around 2 amps was out of fuel territory 4.5 amps about right and 6 or above was a sticking / seizing pump or severely blocked filters.

I was always amazed at how many electric pumps could be revived with a couple of well aimed wacks on them or the underside of the the tank if they were internals.

It's a shame no one sprayed easy start up the air intake last night while it was in a no go state to 100 % prove the lack of fuel theory.

[1970mgb]

Interesting-you might have the first issue I've actually heard of with a Hardi pump. They're generally considered pretty robust, but crazier things can happen.

One thing I would caution checking for is making sure you're not getting random bits of crap on the screen in the tank or elsewhere in the pickup or fuel line. I've had that happen to me a few times, often combined with letting the tank get too low(my fault) and less than great fuel.

I remember driving to work one day when I had a sort of similar situation to you(although not nearly as bad). The gauge was reading 1/4, and I SHOULD have filled up before leaving but didn't. In any case, I was going ~60mph on a steep-ish ramp, and when I got to the top I felt it start to falter and lose power. I limped along to the next exit, and by the time I got down I had just enough momentum left to coast into a spot on the street. I thought I'd run out of gas completely, and a kind soul stopped, asked what was going on, volunteered that he only lived around the corner, and would be back in 5 minutes with a tank. In the mean time, I managed to get it started again and moved into a lot off the street. The guy came, added 2 gallons, and I figured that would get me 3 miles to the next gas station(which is by work). It petered out again by the gas station and I ended up pushing it to a pump. With a full tank, it started right up again, and I drove it a half a mile to the parking lot.

I was convinced that the fuel pump was failing, so went out over my lunch break intent on swapping my electronic SU for the Facet I had in the trunk then. I unhooked the line from the tank, which should have had fuel flowing out of it when I did. I got barely a dribble, but then what I'd best describe as a big rusty brown splooge wad shot out and it started flowing normally. I hooked the line back up to the pump, and everything was fine.

The best I can figure, it was still pumping through the blockage, but just not enough to keep up with a running engine. If I let it run for a minute or two, it would fill the float bowls and let the engine run sort of normally for a couple of minutes.

I had another time where the line from the tank to the pump had decide to collapse(I had it bent gently, but it decided to crimp) and I had much of the same symptoms.

So, I guess I'm just saying it's worth checking all that sort of stuff.

[LightBulbFun]

5 hours ago, SiC said:

only pulling 4 amps or so when running. Hardly enough to be too much of a draw on dirty contacts for it to fail on a short run.

as a side note, 4A is about how much current a Headlamp bulb draws, and seeing how bad they can get with dirty contacts/bad wiring (4x12=48W so near enough 50W)

so id say still check your electrical connections etc, it IS a lucas system afterall LOL

[SiC]

as a side note, 4A is about how much current a Headlamp bulb draws, and seeing how bad they can get with dirty contacts/bad wiring (4x12=48W so near enough 50W)
so id say still check your electrical connections etc, it IS a lucas system afterall LOL

Difference is the duty cycle of a lamp is 100%. The pump is nowhere near that. At full chat it's more like 60-80%. Normal use it's going to be 10-20%.

[LightBulbFun]

2 minutes ago, SiC said:

7 minutes ago, LightBulbFun said:

as a side note, 4A is about how much current a Headlamp bulb draws, and seeing how bad they can get with dirty contacts/bad wiring (4x12=48W so near enough 50W)
so id say still check your electrical connections etc, it IS a lucas system afterall LOL

Difference is the duty cycle of a lamp is 100%. The pump is nowhere near that. At full chat it's more like 60-80%. Normal use it's going to be 10-20%.

and the duty cycle of a set of indicators is only 50% and iv seen bad grounds etc wreak havoc on those (and if you were going up hill when it died, that would indicate the pump was working harder so drawing more current for longer...)

seems silly not to check the electrical connections etc just as a matter of course  unless they are a PITA to get to or such (where it would be a case if you have dug it out, you may as well replace it entirely)

[SiC]

Getting the garage to replace it for me on Monday. Going to go with another Hardi unit as it'll be an easy straight swap. Did say to check the wiring and any blockages before the pump was completely condemned. Thinking about it, the steel braided hose to the pump was from MSC. I'd hope it was Ethanol compliant, but I bet it's not.

 

Out of my four cars (if we exclude my wife's Audi A4 which she's using tomorrow), there is only one left which is fully working to get me to Haynes tomorrow. The ever reliable* and trustworthy**...

[SiC]

2 hours ago, Joey spud said:

It's a shame no one sprayed easy start up the air intake last night while it was in a no go state to 100 % prove the lack of fuel theory.

The RAC sub contracted it out to Victoria Recovery. A friendly youngish chap came out in the van to fix it. When he opened the bonnet, his first question was "Is this the same engine as in the Midget?". He pulled the distributor cap off and remarked that it all looks like new parts. 

At that point I knew it was going to be best to recovered back to the garage. ?

To be honest, it was getting dark at that point and the lights on the MGB are currently atrocious. So getting transported back was a much safer option. 

Incidentally the old boy at the garage who did the work reckoned it would have been ok to RDT it. Said that in the 35+ years he has been a mechanic, he has had many hundreds of cars with overdrives on towed in and has never has seen one been damaged because of it. Something I will have to remember for next time.

46 minutes ago, 1970mgb said:

Interesting-you might have the first issue I've actually heard of with a Hardi pump. They're generally considered pretty robust, but crazier things can happen.

I have heard others on here report that they've had Hardi units fail. I'd never completely rule a unit going faulty. However it hasn't been heavily stressed on my car. Almost never used in the wet, temperatures here pretty much have been under 30C and it lives under the car in the cool.

I always remember chatting to the guys in my local Moss shop and he said that the single one type of item they get back the most is fuel pumps. Every single type they have ever stocked has had plenty of failed items back. I've requested the old pump back if the garage replace it, so I'll pull it apart and see if there is any possible reasons why its failed/failing. Out of all the pumps that are stocked by Moss, the Hardi to me felt like the nicest made unit.

I'm not entirely convinced its the pump itself just yet. My suspicion is that something make have been sucked through and blocked the pump or pipework somewhere. I did fill up last weekend, so possible something got in then. Was from a small Esso garage and I always fill up with Super Unleaded, so also likely to have had less fresh fuel in that underground tank.

[captain_70s]

Bummer. At least you've got somewhere to start though.

Back when the Doloshite started refusing to start the pump was the first thing I replaced. Never could get to the bottom of the issue so the car went in the shed for months as I couldn't be arsed looking at it. Turned out it was an ignition issue and that the brand new pump was D.O.A and the old one was fine...

[SiC]

3 hours ago, Joey spud said:

I'm not saying it isn't the pump but with my ex Rac patrol hat on i wouldn't of said 4 amps is too far off the norm.

Sorry just realised what you meant. I badly worded (as usual) my post. I measured 4 amps on the bench for the pump and what I meant was that 4 amps flowing through the wires/connectors shouldn't be too much of a big deal for them really. 

Either way, I'm leaving it to the garage to fix. One of those things right now in my life I can't be arsed dealing with and rather outsource. Unfortantly it means that this months budget for car fixings has well and truly been used up by the service on this, all the bits to fix the Boxster and now the fuel pump. So the Boxster will have to wait till next month for its quota of the budget repair allowance. I'm trying to be a bit more disciplined on my spending. When you only have 2 or even 3 cars, it is a bit easier to ensure they're all 100% ready for the road. However I've quickly learnt you can't comfortably do that (at least for me) when you have a small fleet. Also less of a need to because you don't need them all working at the same time!

[busmansholiday]

2 hours ago, SiC said:

When you only have 2 or even 3 cars, it is a bit easier to ensure they're all 100% ready for the road. However I've quickly learnt you can't comfortably do that (at least for me) when you have a small fleet. Also less of a need to because you don't need them all working at the same time!

Yon now know why my green MGB GT is still in the garage (after nearly 10 years) winking at me and the mig welder every time I go in there.

That though has a modern, electronic fuel pump, guess why!

[SiC]

8 minutes ago, busmansholiday said:

Yon now know why my green MGB GT is still in the garage (after nearly 10 years) winking at me and the mig welder every time I go in there.
That though has a modern, electronic fuel pump, guess why!

Unfortunately my solid state electronic fuel pump didn't save me this time! All this MGB distraction has made me loose two days of calm, dry weather which would have been perfect for welding the Dolomite in. ?

[SiC]

Got the car back today with a new Hardi pump on. Didn't manage to speak to the guy that did it, so not sure exactly what was done. Hopefully it was properly diagnosed. If not, it'll be going back for them to sort again...

I pulled the pump apart. Couldn't see anything obviously wrong with it. The electronic driving circuit is pretty symbol. Looks to be a Darlington pair driver connected to a 4000 series IC - probably a Schmitt trigger set up as a debouncer. The solenoid position is done by a switch, which is a bit of a disappointment. I was expecting optical or magnetic to make it fully solid state. Contacts are ok but they do wear and get dirty.

Basically these pumps are essentially SU pumps with driver electronics on the end. The driver electronics is like a mini version of a ignition points assistor.

Here are some pics from pulling apart.




You can see the points here


Diaphragm like an SU


Bottom is a cavity with two small plastic discs on the input and output that acts as valves


Close up while actuating it

[1970mgb]

Wow, the microswitches in the Hardi are a bit of surprise.

AFAIK, the solid state SUs use a hall effect sensor. I don't know that 100% for sure-I'm not inclined to pull mine off now and look, and the person I can think of who would know passed away last year. Still, though, it's been tossed around enough that I'm PRETTY sure it's the case.

[Mr Pastry]

If the Hardi pump has contacts which wear and get dirty it can have no possible advantage over the SU pump that was specified for the car.  Which is quite reliable.  Just use the correct parts.

 

 

 

[1970mgb]

1 hour ago, The Mighty Quinn said:

That pump looks like 50p's worth of Chinese crap.  Can you not buy new SU pumps now? Burlen Services took over the SU name iirc and make new SU carbs.

SU/Burlen makes new production pumps of both the points type and the electronic type.

I have the latter in my MG, and it has worked perfectly for quite a few miles and about 4 years now with it pleasantly ticking away. As I said, I understand it to use a hall effect sensor rather than a microswitch as shown on the Hardi above.

[plasticvandan]

I never had any trouble with the original points su points in my minors,and liked the reassuring ticking on turning the ignition on

[1970mgb]

12 minutes ago, The Mighty Quinn said:

Is it not possible to fit a mechanical pump?

 

That Hardi thing looks appalling, badly finished monkey metal shite.

18V blocks have a convenient mounting point for a mechanical pump. A Marina mechanical pump will fit and work fine.

With that said, I personally have an aversion to them, and will choose an electric by the tank if at all possible. My Marina has a Facet brand(noisy cube) pump as installed by a previous owner, and even though I have a mechanical pump in the car just in case(and I know it works) I wouldn't use it unless I was stranded and didn't have any other choice.

New production electric SUs are well made and of a proven design. The points type can have issues in an infrequently driven car(the points can oxidize and cause the pump to not work, a condition often cured by whacking the pump with whatever blunt object is handy), but especially with a TVS across the points can last forever provided that you let the pump click over every few weeks. The electronically switched SUs tend to give years of trouble free service.