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car problem opinions

car problem opinions

car problem opinions

I’m tinkering with a ’73 TR6.

I thought it might be vapor lock problems but I’m now thinking it might be with the mechanical fuel pump. Tested the pump by running starter (no coil) and had 6 psig and spurted fuel.
The mechanical fuel pump is below fuel tank. It has a see thru filter just below the pump inlet in a near vertical position. What concerns me is that after driving a few minutes the filter is nearly empty. The engine sputters with throttle and will not restart when turned off.

Could it be something with the fuel pump’s relief or maybe restriction in the tank supply line?

RE: car problem opinions

Original fuel tank? They tend to rust out.

RE: car problem opinions

I had a Spitfire 1500 and it did have a pro lam with vapor lock. That depends on the fuel and the temperature.

RE: car problem opinions

Sounds like a heap of debris (rust) in the bottom of the tank blocking the inlet to the pump.

New tank needed. You'll never get all the bits out of the existing one.

50 year old cars will basically need to be rebuilt part by part...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: car problem opinions

Check the fuel tank vent as well.



RE: car problem opinions

Moss Motors US is my go to parts store.
LittleInch. . . that is the Europe, fuel injection lay out. Moss also has schematic and most parts for the US carburated version.

some back story. . .
this car was under shed for decades. about 5 years back I got local "low rider" builder to drag it out. they washed out fuel tank, replaced all hydrualic parts (brake/clutch/fuel pump) and flushed engine/trans/axle oil. even after that, it went back under shed. and I just now felt like getting it going.

given I initially thought vapor lock. I have just order from Moss, new lines from pump to carbs, an under carb heat sheald and insulation sleeves from Design Engineering,

when I feel better (than today), I'll drain the tank of about 5 gallons in it through lines from tank to pump. then attempt to remove tank bottom plug.
I'll then try to blow out the tank venting hoses, from tank to carbon canister

I just wanted to besure my think of fuel line from tank. and not something about how mechanical fuel pump works.

RE: car problem opinions

Difficult to tell from here but for me "mechanical" fuel pump means that it is driven off the camshaft rather than electrical. Or is it attached to the engine somehow?

They usually have some sort of in built pressure relief, but its not easy to see what the mechanism is unless you've got a cut away drawing of it.

And how is the tank supposed to vent / allow air in? Little hole in the cap?

But the TR6s are quite classic - convertible?

Under a shed for DECADES??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: car problem opinions

The mechanical fuel pumps were spring loaded diaphragm pumps. The cam in the engine moved a lever that compressed a spring on the suction stroke. The spring force on the diaphragm provided fuel pressure. If there was no fuel drawn the lever did not move.

RE: car problem opinions

thanks . . . the pressure is determined by a spring acting on diaphram....
I was assuming some sort of recirculating relief.
this now enforces the restrictive fuel from tank

this is the tr6 sitting outside the shop. I can't call it a "covertable" as the top was so dry rotted it disentegrated when trying to put down. So it is now a "roadster"

RE: car problem opinions

Quote (LittleInch)

50 year old cars will basically need to be rebuilt part by part...
Especially '70s British ones.
Just sayin'bigsmile

Brad Waybright

The more you know, the more you know you don't know.

RE: car problem opinions

I have seen rust in tanks, fuel filters that were decomposing, fuel lines that are losing their liners, biological growth in fuel systems, and about a dozen other issues.
You need to pull the fuel pump and make sure that the diaphragm is sound. A couple of small pinhole leaks would also cause issues.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: car problem opinions

Sister had a 74 Pinto when in college. This car used a mechanical diaphragm fuel pump on the engine. Engine would sometimes sputter and stall for no apparent reason. Had it towed to the shop a couple times and they could find nothing. She would drive it again a few days, and it would repeat the problem. Third time mechanics took it for a test drive while she waited - and they returned on foot an hour later. Issue was rust in the fuel tank, but the tank was fine. This was during one of the gas shortages and some stations were pumping the dregs from the bottom of their almost empty tanks. There was a small coarse filter screen on the fuel pickup in the tank and it would plug. Towing the car would shake the rust free of the pickup screen.

Isn't the UK in another fuel/petrol shortage situation?

RE: car problem opinions

There have been a few shortages caused by demonstrations outside fuel distribution depots, but it hasn't caught on yet and caused the panic buying we saw last September.

Think Diesel prices are higher now as apparently we used to import a lot of diesel from Russia for some reason.

I had a Mk1 golf which had a fuel pump go down and then when they came to replace it there was nothing coming out of the tank. Same thing - rust and dirt blocking the internal pre filter. So what was supposed to be a £120 repair turned into nearly £800 [and this was 30 yrs ago] as to replace the fuel tank they had to remove the rear suspension....

So what starts off as a simple replace the filter job suddenly ends up as a major exercise.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: car problem opinions

little update.
I m getting where i don't see the onvious sometimes.
I crawled up on the trunk lid and easily can see the condition of the tank. I was surprisingly CLEAN! I used a strong pick up magnet and got NOTHING.

the tank "vent" is part of an evaporitive emmissions setup, so that is something I need to check farther, BUT while driving, etc it is easy to reach back and flip the fill lid open

disconnecting at the pump, I get good flow. roughly the bottom of tank is same level as pump inlet.

I vented the filling of the filter of air on pump inlet. drove about 30 minutes and when I shut off, I watched the fuel filter go empty (less than minute)
the pump is too warm to hold.

RE: car problem opinions

Yeah, the fuel tank needs to vent somehow.
Sounds like this isn't the issue, but the fuel pickup in the tank may/should have some kind of filter sock or screen, Those can get dirty and obstruct flow.
Caution: It may be tempting to blow compressed air back up the line to the tank, but that can blow the filter sock off, allowing crud into the fuel line.
Maybe you can access the tanks side of the fuel pickup? New filter socks are pretty cheap.

Jay Maechtlen

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