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TR2/3/3A Excessive cranking before it starts.

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DavidApp

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On my newly rebuilt TR3 motor I have started to notice that if I leave it sit for several days or even over night when I go to start it it cranks for about 15 seconds or more before it starts to fire. Once it has run for a few seconds it will fire as soon as it starts to crank.
I am presuming that the mechanical fuel pump check valve is allowing the fuel to drain back as it sits and that I need a new pump or a rebuild kit.

David
 
TomMull

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Assume choke is working properly? I'm not sure the pump even has a check valve but the question is somewhat moot as the pump is kept filled by gravity.
Tom
 
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DavidApp

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Hello Tom

Yes the choke works and that does not improve it till it starts to fire. I do not have much gas in the tank at the moment. A couple of gallons just enough for testing. So the line to the carbs would be higher than the level in the tank.

David
 
CJD

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When these cars sit, the fuel bowls evaporate all the fuel. Sitting over the hot exhaust manifold, it is almost like holding the carb bowls in an oven! 15 seconds is about right for the bowls to re-fill. Remember that even if the fuel lines drained back to the tank, the bowls cannot siphon back, and as long as the bowls have gas the engine will start. So that is not the cause. It's evaporation. This is undoubtedly why the fuel pumps have manual pump levers. I always pump the bowls full before starting, and the engine fires right up, hot or cold.
 
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DavidApp

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Hello John

Thank you. You get use to modern cars firing right up so the cranking like that was a little concerning. An electric pump would help with that.

My pump does not have the hand pump lever. May have to get one from Moss and keep the old one as a spare.

I do have the heat shield but that can only do so much.

David
 
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pdplot

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IMHO 15 seconds isn't bad after sitting. My TR6 takes about 20. Used to be more until I reset the choke, make sure it's opening all the way. Also check your point gap. Should be about .015. I actually still have my little Lucas tool with the .015 feeler attached.
 
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sp53

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My car starts right up after weeks. Maybe 4 seconds after a few weeks. 15 seconds in the climate I live in is way too long for me. Pull your plugs and look for carbon often as you sort the car problems out and make sure the choke pulls down like at least ¼ inch on both carbs maybe a fuzz more. Make sure your coil is not hooked up backwards and that the points are clean with no white film with an exact 15 setting-15 is not much and difficult to see for me. I use a dwell meter after I set them with a gauge. If you have a second dizzy, put that in and see if it makes a difference. Also I have found the metal wires make a difference. Get good ones like at Nappa that are made up from the manufacture are better. The aftermarket ones that we need to put the plug ends on leak and give weak spark.
 
PeterK

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Since it's rebuilt recently, check your float levels in the carbs. Mine were low, same symptom, I used the priming lever. Now after adjusting, it fires up within 5-10 seconds, mostly (haha).
 
trglory

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When I leave the car sit for any extended length of time, I pop the bonnet and fill the pots back up with the priming lever on the fuel pump before I turn the key and push the button.
 
TR3driver

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The float bowls can't drain back through the pump, even if both valves in the pump go bad.

My guess is that either the float bowl mounts, or the lower jet gland (or both) have started to leak just a bit. They often can leak so slowly that it doesn't even drip (just evaporates), but still drain the bowls.

Reach under and touch the head of the bolt (or nut on some H6) that holds the float bowl then smell your finger. If you can smell fuel, the mount is leaking. Repeat for each jet.

My experience was that the cork gland seals would only last about a year of daily driving. Nitrile O rings last a lot longer.
Adding a heat shield helps the bowl mounts last longer, but they're still only good for a few years.

The good news (?) is that with practice you can change the seals without removing the carbs. Still have to recenter the jets, though.
 
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DavidApp

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Hello Randall

I hope that is not the problem as the carbs are fresh back from Joe C in New York so I would expect that everything should be right.

I will check for gas where you suggest.

David
 
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sp53

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Why would you have to re-center the jet if you are fixing the bowl attaching seals, Randall? I do not have a heat shield, but from the pictures I have seen of them they look like they would block most the view of the carbs. I would take it off until I had connections tight because like Randall suggested those seals leak easily and will vibrate loose and drain the fuel. If you look at the Moss catalog, you will see the tr2 used a brace to stop the bowls from shaking around. I made some of those braces for my braided lines bowls because the older braided line set up rattles from the banjo bolt and line weight. I can usually get many years out of the seals that way, but yes that is a good place to look for a leak. You might go under the car and look up to see if you do have a leak. I believe you have something wrong. Perhaps a cold starting problem from weak spark or a combination of few things, but 15 seconds is a long time for a cold start that will wear out the starter and battery
 
TR3driver

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Sorry, I wasn't clear. Posting from my phone and got distracted. You don't have to recenter the jets if you just change the bowl mounts; only if you change the cork gland for the jet (which requires removing the jet housing and hence taking apart the adjustment).

Yes, the shield does block access to some extent, but it hasn't really been an issue for me. Doesn't really block carb access at all (except for the vacuum line), just the starter and generator.
krOhZOv.jpg


FWIW, here's a shot I took while installing mine. This bowl mount is only about a year old and looked to have been cooked by exhaust heat.
9BsLP27.jpg
 
TR3driver

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Could be, I can't prove it. But the ones I left on the shelf sure didn't look like that!
 
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DavidApp

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After checking a lot of things and changing some with no change I found that if I dropped some gas in the carb mouth it starts right up,.

The carbs are newly rebuilt by Joe in NY so I did not doubt them but I checked the float levers with a 7/16" rod and there were exactly right as I expected. The valves worked, I blew through them .

Cranked the motor over with the gas line off the carbs and got good flow and there was pressure if I blocked the line while cranking.
Put my emergency electric pump on and the car started right up.

Must be a failing pump or it does not produce enough pressure. Just ordered a new pump from Moss.

David
 
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TFB

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If you have the filters off to add gas,lift the pistons and you should be able to see the fuel level in the jet,which should be just below the top.Then you can cross float adjustment off your list or readjust as needed,but sounds more like a leak as mentioned.
Tom
 
Graham H

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Hi David,
I would still be a bit sus of the choke working properly, can you pull it all the way out and take a photo and post so we can see if it is pulling the jets all the way down.
If the fuel level in the float bowls is at the right level it should start,as you know SUs will not start from cold unless you pull the choke out. It allwas amuses me when i see vidio of someone pumping the pedal on a vehicle with an SU carburettor:fat:

Graham
 
TR3driver

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Just to point out the obvious, the stock pump does very little before the engine is running. It should start on the gas left in the bowls from last time. If the bowls go dry, the best mechanical pump in the world is going to take a long time to fill them back up, with the engine only turning at cranking speed.

Still sounds like a leak to me.
 
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DavidApp

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Hello Randall

I do not see any evidence of leaking. I will recheck in the morning with a flashlight.

Graham

I did notice that when the choke pull is all the way out the choke lever on the carbs will move a bit more. A lot of the pull movement seems to involve straightening the choke cable outer. With the choke pushed in there is a loop in the cable when it is pulled the cable is almost straight I do not think that I can take up any more slack at the attachment point. You need a tiny bit of slack to insure the choke is all the way off?
Shorten the choke cable or restrain it somehow?
Interestingly when I held the choke fully pulled at the carbs and started it did start up almost immediately.

David
 
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