OK guys.I think the problem has been solved! I had already checked all the wiring and although I hadn't ruled it out, I thought long and hard about the fuel issue and as usual, the problem was quite logical.
As nothing had changed, even with a custom stainless tank and presumably no rust, I wondered about the occasional batch of crap fuel.The car has an engine mounted mechanical fuel pump so I thought more about the front end as I had a hunch it wasn't the tank, but I did go armed with a spare electric pump, some hose, clips and had, by the time I'd read the above posts, been persuaded that it was a fuel issue.
I had an inline filter between pump and carb and decided to renew it, even though it wasn't very old.
I nipped to Repco and bought a new filter.I just happend to show it to Mal at By'Gone for his opinion, and he pointed out straightaway that the outlet wasn't the ideal size and found one on his shelf with a larger oulet.
I am pleased to report that today, even though outclassed by the majority of the field (my paltry cooking 3 litre is no match for sports racing cars or 680bhp Corvettes.) the car pulled like a train and no sign whatever of what was indeed fuel starvation.
So a big thank you for all who contributed and made me think long and hard about it.I do appreciate all your input.
jsbike,
Jan 21, 8:39am
always good to hear back from posters when they sort it!
socram,
Jan 23, 3:06am
Parents always brought us up to remember our manners.
skin1235,
Jan 23, 3:20am
so simple to fix huh, so hard to find someone above said the tribulations of driving a 40 yr old car beyond it's design or words to that effect but this was an everyday part that let you down bet you won't get caught be that again
as jsbike said too +1
1fordluva,
Jan 23, 5:16am
great stuff! makes the racing alot more fun.
socram,
Jan 23, 7:41am
Well it would have made the racing more fun if the weather hadn't wiped out today!
socram,
Dec 13, 7:50pm
Racing at Hampton Downs at the weekend. Car running well for most of each lap, but at the long fast 180 degree right handed sweeper, 2/3rd of the way round, accelerating hard in 3rd gear, engine died, then restarted OK after a second or two.Rev counter naturally enough swung from 4,000 back to zero and everywhere else on each lap, all was great.First time it happened, I pulled off on lap two.Second time it happened, pulled off again.Last race decided to stick it out and finished the race, albeit at the back (handicap race) - it happened 4 laps out of 8.
Car has twin Strombergs, electronic ignition, and is basically 100% bog standard cast iron Volvo B30 straight six.Oil in dashpots OK.No evidence of loose wires or leads.
I have owned the car for 20 years and have never had this sort of problem before.
Difficult to find, as when the car is stationary it is fine and it only happens on a corner I have taken dozens of times before without problems.Even gave Trog aride round the previous week with no problems!
Can't believe it is a tank fuel problem, (tank sis baffled) but maybe the engine mounted mechanical fuel pump is getting tired!Maybe I need a bulkhead mounted fuel filter with a bit of a reservoir! ignition system - slightly loose wire! Where do you start with this sort of problem!
It was rather warm at HD - 31 degrees and although water was OK, oil temp was quite warm.
Any suggestions anyone!
maddrexx,
Dec 13, 8:23pm
just go thru the wiring system and fuel system with a fine tooth comb
skin1235,
Dec 13, 8:40pm
clip that loom down at every possible place, I'd say it is swinging due to momentum/inertia and open circuiting somewhere being that it appears to be in the ignition circuit maybe try a small buzzer at the terminal point and gently twist pull push the loom listening for the buzzer to falter, and it could just as easily be an earth point well away from the expected ignition system, check all engine earths, and even dash earths do you have to have kill switches on your class, (toggle pole pulls to strap), could even be a complete electrical fail due to a worn or inconsistent contact in the main switch
what expected time frame to negotiate that corner, if less than 3 or 4 seconds I'd say it won't be fuel starvation, but a clear line in view will show if it's pumping air ( great fun for a co-driver, first you have to get his eyes off the windscreen and back to the hose, and his adrenalin levels back to allow coherent thought and speech, while hanging onto the frame for dear life ( no spare seats in there)
carkitter,
Dec 14, 2:07am
T-piece the fuel pressure line and run an extended hose into the cabin to a fuel pressure gauge. Have a passenger monitor it if necessary.
tmenz,
Dec 14, 3:11am
When my car cut out suddenly and the tachometer dropped to zero, it turned out to be faulty ignitor module in the distributor. It came to life a couple of times when cooled off but failed again - intermittent component somewhere - new ignitor fixed it!
socram,
Dec 14, 4:55am
Last first - sump is baffled (so is the fuel tank) and as per OP, the problem has only just surfaced. Lack of oil would not cause a total misfire. Oil pressure is good.
The fact that it is only on one long corner is the telling factor I think.
Stromberg carbs do carry fuel, but why would they suddenly develop a fault!
I am leaning towards a dodgy wire connection somewhere or as above, something in the electronic ignition system as a last resort.
Fuel starvation is usually more gradual as one carb dies then the other.
The difficulty is testing it unless something is found that is obviously wrong.
Thanks so far, as someone often comes up with something I hadn't thought of.
clark20,
Dec 14, 5:28am
Did you say Tacho went to zero, I would say electrical, but check engine mounts etc, under hard cornerings things move more than you think, might be shorting or pulling a wire, and the wire can break inside the insulation.
socram,
Dec 14, 5:53am
Thanks bob1120. As the first occurrence was with 25 litres of fuel, I have ruled that out.
I think that clark20, you might be on the money there.Although much of the wiring was renewed 1994 when I restored it, there would be some original stuff in there.I'll probably start with the coil wires.
saki,
Dec 14, 6:16am
I would go with skin, 20+ year coil or module wiring
peril787b1,
Dec 14, 6:26am
Sounds like a similar issue I had with an 82 Mazda Cosmo. Occasionally, and very randomly, it would completely die and then just as suddenly spring back into life.It turned out to be (after 4 hours with an auto sparky (long time to find, 5 minutes to fix) a cold solder joint (from factory) that was breaking power supply to the coil. It was "found" when the sparky dropped his multimeter onto the loom and the power cut out.
dent,
Dec 14, 6:27am
I would agree with the ignition side of things. Specially considerring yourd still have it in gear therefor the engine would still be turning otherwise if it wasnt it wouldnt havent restarted. And if the engine was still turning and the rev counter droped it points to ignition.
kwkbrk,
Dec 14, 6:37am
Mates V8 Commodore does EXACTLY the same thing in EXACTLY the same place. Solution : Keep the fuel level up, in his case over half full. Worked for him.
socram,
Dec 14, 8:30am
The very fact that I have been running at HD for over a year now - often with low fuel and never had that issue means that the ignition wiring side is still number one suspect rather than fuel as nothing on the fuel system has been changed.Wiring however degrades and is often subject to zero external tell tale signs.
I am intrigued at the fuel vs ignition/electrical camps on here which just shows that these sorts of hiccups are never 100% straightforward even for you experts -and if there is one thing I have learned over the last few years is that even the best experts differ - which is not a problem.
#12 - love it! Exactly why there is so much hit and miss with diagnostics.
clark20,
Dec 14, 8:35am
Hey Socram, what times are you doing, mate took his X5 M out and did 1.24s, but not pushing too hard, whats that time like!
fordcrzy,
Dec 14, 8:43am
does the car have a low oil pressure switch thats connected to the ignition so it cutts out if oil pressure drops! even though the gauge shows good oil pressure they are made to be slow responding, so you may be getting low oil pressure at the switch while the gauge shows ok.maybe try bypassing the oil pressure switch!
smac,
Dec 14, 8:46am
Not 100% sure what you meant in the original post about "Rev counter naturally enough swung from 4,000 back to zero".
If you meant that the rev counter behaved naturally enough the whole time, then you have a fuel starvation problem. I know zip about strombergs but if they have any kind of float in any kind of bowl, start there. If the rev counter drops to zero when the engine dies, then yeah you have a loose connection SOMEwhere. Finding them can be a pain. Have had same symptom before, eventually found as a loose dizzy connection that was separating under certain G's.
socram,
Dec 14, 9:06am
The rev counter was stable with no flicker at all when running.
Why a fuel starvation problem when it revs in a straight line and through the hairpins!There is an inline filter close to the carbs and that usually acts as a small additional reservoir.
The long corner certainly sends fuel outwards but the baffled tank means that it still picks up fuel. The engine is extremely heavy and maybe is moving a fraction on its mountings and a wire may just be stretched but note that it didn't do it on every lap!
It could be as simple as an ignition switch wire.
smac,
Dec 14, 9:18am
Have just taken a crash course in stromberg's (OK I looked at a pic!). Seems to be a very similar situation to an SU - in a high side-load situation the float can fall/jamb sideways and fail to open the jet/valve properly, the bowl empties and engine dies.straighten up (or even just slow down), bowl starts to fill, and you're away. If this is the problem then it's probably doing it in the hairpins as well, but the float bowl holds enough to get you by. In a loooong corner, it runs out.
If you have an electric fuel pump you can test this: invoke the fault (ie thrash it around a sweeper) and when it has died, switch off the ignition and coast to a stop. Open the fuel bowl, if it's close to empty, bingo (it won't be completely empty as some will siphon through when you slow down.
The SU's were majorly redesigned to prevent this very issue - they went from a side mounted fuel bowl to one in the carb body it's self.
If the rev counter is not flicking to zero I would assume not an ignition fault (for now).
socram,
Dec 15, 4:44am
That is a very sensible post.Thanks.
Carbs were replaced with a newer set and professionally overhauled not too long ago, but your explanation does make sense.
Unfortunately, replicating this sort of thing other than on the race track is not exactly easy to do!I may have to go down for the track day on Monday.
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