Strange engine problems

[Orsom Weels]

After all that, I would say you have petty much eliminated any problems with the fuel tank & supply line & it sounds like both the fuel pumps you have work OK off the car, so, just for a moment, can we forget about fuel & concentrate on ignition, in particular ignition timing. You say with your mity-vac supplying fuel to the carb's, it started but ran badly for a few seconds, but would not then re-start. Did you check ignition timing before & after that attempt? You need to be certain that your timing is correct & staying that way. If it IS moving in relation to the crank & cam shafts, the best you will get is pops & bangs. If the problem is with the jack shaft, you should be able to prove it at this stage. After you have eliminated any problems in that area, you can start looking for other faults in the ignition system. Once any have been found & rectified, the engine should run with your mity-vac supplying the fuel, if it won't, then you need to look at the carb's to see if there are any blocked jets etc or bad air leaks. Once all that has been sorted, then you can worry about why the pumps won't work on the car.
Regards, Tim

[Chancer]

I thought it was a hand hald Mityvac you were using, I had always meant to buy one and your posting prompted me to bid on one on E-bay, I didnt realise that the bigger one could pump as well as suck, its a shame as I have recently bought a suction pump for o?l changes.

If the fuel pump valves are in the correct orientation then you should be able to pump right through the fuel pump.

Its possible that the problem is one or both of the float valves are stuck.

I am going to disagree with all those that think you should jump to ignition fault finding, the only thing that (I believe) we can safely say is that you had/have a fuel starvation problem, it may not have been the pump but could be the floatvalve(s), that is what I would check next, continue using the Mityvacto pump through the fuel pump until you are sure that both carbs are filling correctly, if it still wont run properly follow the last lot of advice, check the timing, try running it again and check the timing once more.

good luck.

[mbell]

Presuming this is webber the first thing I do is check the fuel level on the carbs, too high or low and you'll get bad running.

It will take a couple of mins to do. Remove the jet cover, one each carb, remove the main jet assemble for one barrel. Get a small screw driver/pointer and mark it or tape it at 25mm from the point. With a light shinning down the jet holder and insert it until you see the shimmer of it hitting the fuel. The 25mm mark should be directly inline with the top of the jet holder.

If the fuel level isn't at 25mm on either carb you'll need to adjust (bend) the float tab on the lid, which will be a guess/trail repeat type process until you get it right.

I'd be tempted to suck some fuel out of the carb body and reconnect a pressurized fuel source to make sure you are checking them as the operating level not just whatever level they happen to be at.

[Heuer]

The car has Strombergs. I have both the large Mity-vac and the smaller hand-held version which is great for bleeding the brakes without an assistant. There are several versions, some with vacuum only, others with vacuum and pressure (up to 30psi):


Just rechecked the timing after the car ran badly and stopped - the timing seems to have changed.

[billwill]

It may be as trivial as the clamp on the distributor stem not being tight enough, but take care the moulding of the distie is thin and I seem to recall mention on this forum of someone cracking the distie stem by doing up the clamp too tight. I suggest testing the clamp on the stem on the work bech while both are off the engine. Some members have designed/constructed improved clamps, I seem to recall.

If you have a strobe timing light and if you can get the engine running long enough, you may be able to observe the timing changing.


~~~~~~~~~~~~~

See:
lotus-electrical-f38/distributor-clamp-solution-t26079.html


It seems that improved clamps are available from Q.E.D.
http://qedmotorsport.co.uk/qed-shop/vie ... istributor




Lots of stuff on this forum itself about Disties & their Clamps.
http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

[twincamman]

I hate to suggest this ..but could your crank shaft be broken
????ed

[Heuer]

170psi on all cylinders would suggest the crank is rotating.

[twincamman]

OK ..just a thought ......if it won't fire on ether then it's electrical ....even when the timings out it should back fire .....just my opinion ..pull lit and rebuildthe engine if it sat that long without running ?..you will only have to do it later anyhow when it self destructs ..its not that big a job .ed

[Matt Elan]

Been reading this one with interest. From my observations, it would seem that there is adequate fuel getting to the carbs, and that hasn't changed the issue which is the backfiring and poor running. Compression is good on all cylinders. Carbs were fine before the issue and appear OK still. The only carb related problem I can think of is a split diaphragm on one carb but I not sure that would show all your symptoms.
So I'm tending towards ignition or jackshaft/dissy drive failure.
So before we blame the jackshaft, there are a couple of things that I would do:
1. is the distributor properly clamped to the block and not moving?
2. Is the timing set correctly?
3. Are sparks getting to the plugs?
4. After trying to start the engine, have any of the above changed?

If nothing has changed then I'd suspect that its an electrical issue. I'd look at the electronic ignition system; if its not electronic then I'd suspect electrical components - coil, condenser, ignition switch and any associated earths.
If the timing has slipped but the distributor body hasn't moved then there is an issue with he distributer or the jackshaft. This could be a broken jackshaft or a stripped dissy drive gear or the dissy drive gear is spinning on its shaft.

However, never forget that 70% of electrical problems turn out to the carbs, and 70% of carb problems turn out to be electrical

Just had a thought - have you put new spark plugs in? The old ones will be fouled by now and it appears on modern plugs the insulator is not glazed all the way up to the body making them more likely to foul up. My 1970 Triumph Bonneville can be a pig to start if its been left standing - new or cleaned set of plugs stops it misbehaving.

HTHs
Matt

[Heuer]

Having exhausted everything I could think of I had the car transported to Paul Matty. They put in a new fuel pump and with a small tweak of the timing the car ran perfectly. Just drove it the 80 miles home without missing a beat. They are at a loss to explain why I had those symptoms and I am at a loss to explain why the car is now running perfectly. Maybe the bouncing around in the transporter freed up a stuck carb float?

The first replacement fuel pump did not work because when I moved the top plate so the inlet/outlet were in the correct position it seems I did not fit the diaphragm properly.

[Heuer]

A follow up to this thread. After Matty replaced the fuel pump we were able to enjoy the Elan. It was put in the garage in September and last week I had to get it out for its MOT. Unfortunately the car would not start with fuel in the tank the pump filter bowl was empty. History repeating itself!

I did a suction test on the tank, pipe and pump and fuel flowed easily. Having become particularly adept at removing the pump I had it out but it tested OK on the bench. I got out the original pump than Brian had checked and tested and it too easily pumped fuel on the bench. I reinstalled the original pump but no fuel appeared in the bowl. My current theory is the pumps are sitting too high and the cam is not working the lever through its full cycle. When turning the engine over without the filter bowl and pipes the pump is not making the pok-pok sound it made on the bench - more of a phtt-phtt. When Matty fitted the new pump they must have got lucky and it was seated low enough to work. Over time or with some wear the pump must have moved slightly (the bolts were not that tight) so it is not fully cycling on the cam. Because of the location I can't keep a constant down pressure on the pump whilst tightening the bolts (the cam pushes it upwards against the spring). I have left the original pump in situ.

I have given up and fitted a Facet 60104 Posi-Flow Fuel electric pump:


Only took a couple of hours including the wiring. Pump earth went to earth lead on tank sender. Ignition switched/fused supply teed from green cable going to VR on back of the tachometer. Cable run under centre console and following the speaker wires into boot. The pump is currently mounted via a couple of self tappers and some chassis damping material. I have the rubber bobbins so now I know everything is working I may refit the pump with them to further reduce noise. A 3A in line fuse will also be fitted.

[Chancer]

It could have been a valve problem allowing the fuel to drain back and/or the pump not being able to prime.

I would have connected the fuel lines to it and actioned it by hand in the engine bay to see if it would pick up fuel, if it would not after maybe 10 strokes then your hypothesis would be proved.

Back in the day many of the pumps had a priming lever attached so maybe fuel draining back was always a problem or just evaporation, in any case it would only take 2 strokes maximum before you could feel resistance, a couple more to fill the glass bowl and a few more to fill the carbs at which point the resistance increased, if you never felt resistance there was an air leak in the suction side or no fuel in the tank.

[Heuer]

Actually I sucked fuel though the pump until the bowl was full, reconnected the carbs and tried to start the car to no avail. On the bench two strokes did indeed bring fuel into the bowl. I then connected it to the tank with a bit of hose, it primed and filled the bowl. So the only part not tested was the fuel pipe and connector to the fuel pump although when I sucked fuel through there were no bubbles. With the electric pump there are no leaks which leads me to the cam/lever problem as the cause.

[Chancer]

back in the day some fuel pumps had spacer blocks which as they were non metallic may also have served as insulators, if you fitted the wrong pump with the wrong arm to the wrong vehicle it would cause the sort of problem you had.

Fast forward 40 years and all knowledge of what would fit what and what wouldnt has all but been lost, with the greatest of respect to many of the suppliers they may not have that specialist knowledge and are reliant on their suppliers who are probably themselves resellers, add to that the fact that repro stuff only seems to need to resemble the original, , the emphasis is on what will sell the ability to function being low down the list, I would not want to be a specialist parts supplier in this day and age, their reputation goes out the window with peoples use of social media and its not them producing the rubbish, were OE quality parts still available there is no way they would sell fuel pumps that dont, or donuts with the same strength as jam doughnuts but e-bay would be full of them.

[Heuer]

The pumps (now numbering three, one original two brand new) are all correct and have the matching insulator/spacer. I will be checking this anyway because in my excitement to get the electric pump installed I had forgotten I had not put Hylomar on the spacer gasket - so big oil leak! I assumed I would be removing the mechanical pump yet again to diagnose the problem so had dry fitted it.