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GT6 Fuel issues - hard to keep running

Richter12x2

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Well, after being more or less parked for 3 years and stalled (due a disagreement with the wife over paint, and life happening) the State of Texas has decided that we need to get the Triumph running again.

Apparently, beginning this year, we're not allowed to register a car without also getting it inspected. Since we're grandfathered in to the Year of Manufacture plates for a Classic Car registration, if we let the registration lapse at all, then not only will we (according to the law) never be able to use those plates ever again, but we'll also be unable to register any OTHER year of manufacture plates as a Classic Car, but would have to register as an Antique (which limits your mileage and use to only to and from shows, exhibitions, and the workshop.)

So we've basically been given about a month to get it running, and drive it down to get an inspection. Hopefully it will make it back this time (last time it made it there, passed inspection, and then had to be towed home.)

After printing off the checklist, and fiddling with some wires, everything looks perfectly fine for the inspection, but I'm running into issues keeping the car running. Initially we had installed an electric fuel pump, and bypassed the brand new mechanical one, adding a fuel pressure regulator to keep the psi down. After testing this time, it was DOA. The replacement 42S Mr Gasket model was $50, so they recommended a much better built replacement, that ended up being very loud, and constant, which made me feel like it was overrunning the regulator.

So right now, I've actually disconnected the electric pump, and bypassed it with a hose. I'd rather use the mechanical fuel pump, if possible (I'd added the electric when I was troubleshooting my previous issues, which turned out to be an incorrect carburetor spacer.) It seems like it's just not pumping enough gas - it usually starts fine on choke, and dies a bit after turning the choke off (although it sounds good after turning the choke off - no chugging, just smooth idling engine).

If I prime it by hand, it'll run for 3 or 4 minutes, unless I open the throttle, then it dies quicker.

I'm thinking tomorrow, I'll pull the line from the fuel pump, and push some air back through into the gas tank - hopefully it's just something gumming up the lines a bit. We had drained the tank for storage, but it's not really possible to get everything. Hopefully that'll resolve it.

Mostly I wanted to post because while I was browsing and searching, I didn't see very many GT6 prefixes out there, so I wanted to represent a little. :smile:
 

Don_R

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Richter,

what carbs are you using...SU or stromberg.....
 

trrdster2000

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Richter, Thanks for keeping a GT6 out of the scrap yard.
The carbs have the spacer and if I remember right, they have a small gap that lines up with a vacuum hole in the bottom of the carb. I feel sure you got it right but the old saying "stuff happens".
Are you running the CD2's of the later model. If just sounds like it's running out of gas or a vacuum leak not allowing enough pull in the ventura. Lift the piston and see if the butterfly might be off center.
Good luck and Texas should be ashamed of that new law. What does the inspecting involve? Brakes and lights? The base in England made me put in seat belts in the '37 MG bolted through a wooden floor board, yeah, that looks good and will save you. The whole car is metal nailed on wood, you better hope it throws your a.. out of the way.


Wayne
 
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Richter12x2

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Richter, Thanks for keeping a GT6 out of the scrap yard.
The carbs have the spacer and if I remember right, they have a small gap that lines up with a vacuum hole in the bottom of the carb. I feel sure you got it right but the old saying "stuff happens".
Are you running the CD2's of the later model. If just sounds like it's running out of gas or a vacuum leak not allowing enough pull in the ventura. Lift the piston and see if the butterfly might be off center.
Good luck and Texas should be ashamed of that new law. What does the inspecting involve? Brakes and lights? The base in England made me put in seat belts in the '37 MG bolted through a wooden floor board, yeah, that looks good and will save you. The whole car is metal nailed on wood, you better hope it throws your a.. out of the way.

Wayne

Haha, exactly. My thinking is they probably intend the law to keep people from getting inspected once and then running around with no sticker for years, but by my way of thinking that's what the police are for. I guess it's harder now since this year a 1991 car can be registered as a Classic, so some people may try it as a dodge.

Ultimately, it's a good motivator to do something we should have done anyway, I just resent being forced to stop everything do it, when I was making such good progress on the Packard. I'll actually have to drag a Packard frame and parts out of the way just to get the Triumph out of the garage.
 

arcom

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Over the past 40 years I've had your problem on two occasions. One in a Lancia and the other a 240Z. Both times it was a clogged fuel filter.
 

Don_R

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Richter,

Had a similiar problem...got some dirt in the carb and it was messing up the fuel flow to the carb...changed the fuel filter and had to pull the float bowl and clean out the needle and seat...all was well after that...
 
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Richter12x2

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Pulled apart the fuel pump and blew out the lines yesterday (both directions) - diaphragm is good, checkvalves are working, and everything inside was sparkly and new looking (Makes sense, it's only been driven maybe 10 miles since it was all installed, and it was a new pump then). I was able to drive the car down off its step in the garage (it's stored in an area the previous owner had built out for wood working equipment, up a 6" or so step, so I have to drive it up and down with ramps and dolly it up against the wall to get into the house.)
It died a few times, but only once I couldn't get it restarted with the key - gave a couple of pumps on the primer and it started right back up again. I really don't want to punt and put the electric fuel pump and regulator back on - is it possible that if the carbs are dialed in too rich, they could deplete the gas in the bowls? They've never been set up officially other than the generic starting point guidelines. It sounds great when it's running though.
 

karls59tr

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Richter,

Had a similiar problem...got some dirt in the carb and it was messing up the fuel flow to the carb...changed the fuel filter and had to pull the float bowl and clean out the needle and seat...all was well after that...

Did you do what Don R said? If the car has been sitting it could very well be the gas filter and and a gummed up needle and seat in the fuel bowl.
 
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Richter12x2

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Yep, that was one of the first things I did. Actually, that's how I realized my electric pump wasn't working, is I pulled the float bowls and realized they were dry as a bone (and sparkling clean besides.) When I stored the car, I drained all the fuel, turned off the fuel pump and let it die off to burn all the fuel in the carbs. So far I haven't seen any signs of varnishing at all.
 
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Richter12x2

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None taken! :D It's easy to forget the obvious. Since it was stored dry, I had to run to the store and fill a 5 gallon gas tank, so about that much. I've worked in support, so I've done a lot of "Is it actually plugged in?" :D
 

karls59tr

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I wonder if its worth trying to run the car from a gas can directly to the carbs to see if would run with just gravity feed thus isolating the pump and pointing to a carb problem. Of course you'd have to take the proper precautions to secure the can.
 

dklawson

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If I remember, your GT6 is early, like mine, so it will have the 150CDs, not CD2s. That's good because they are easier to troubleshoot and adjust.

I'll offer a couple of suggestions. Remove the float bowls again, then remove the floats. Drop the floats in a bucket of gas and confirm that both pontoons on each float assembly actually float. I had a situation where one pontoon sank and the other floated and it caused terrible running problems. With the float bowls removed, put buckets under the open carb bottoms and crank the engine (spark plugs out and disconnected) to confirm that the fuel is getting past the float valves. If you have Grose Jets installed, consider replacing them with Viton tipped "traditional" float valves. Lastly, when putting the carbs back together, pay a lot of attention to the float height. I think Poolboy has posted pictures of the measurement a few times so search for his old posts.

If you have to go back to the electric pump, that's not necessarily a bad thing. If you are using the round, pancake pressure regulator with that setup, that could be a problem. They are notoriously unreliable and inaccurate. The Holley regulator has a much better reputation. If you have a quality regulator it is very unlikely that your electric pump is overpowering the regulator unless you have a fuel injection pump instead of a low-pressure pump for carbs.
 
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Richter12x2

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If I remember, your GT6 is early, like mine, so it will have the 150CDs, not CD2s. That's good because they are easier to troubleshoot and adjust.

I'll offer a couple of suggestions. Remove the float bowls again, then remove the floats. Drop the floats in a bucket of gas and confirm that both pontoons on each float assembly actually float. I had a situation where one pontoon sank and the other floated and it caused terrible running problems. With the float bowls removed, put buckets under the open carb bottoms and crank the engine (spark plugs out and disconnected) to confirm that the fuel is getting past the float valves. If you have Grose Jets installed, consider replacing them with Viton tipped "traditional" float valves. Lastly, when putting the carbs back together, pay a lot of attention to the float height. I think Poolboy has posted pictures of the measurement a few times so search for his old posts.

If you have to go back to the electric pump, that's not necessarily a bad thing. If you are using the round, pancake pressure regulator with that setup, that could be a problem. They are notoriously unreliable and inaccurate. The Holley regulator has a much better reputation. If you have a quality regulator it is very unlikely that your electric pump is overpowering the regulator unless you have a fuel injection pump instead of a low-pressure pump for carbs.

These are good suggestions - I remember setting the float height to 17mm I think with a tiny little ruler, so pretty sure that's accurate, but it's easy enough to check when I've got the bowls off. I can idle the car again until it dies, then the float bowls should be pretty much empty, and if they're full I'll know it's something else as well.

I checked the float pontoons before as well, but that was 3 or 4 years ago, so that doesn't necessarily mean they're good now.

I would have done all this tonight, but of course, with 0% chance of rain in the forecast for the rest of the week, the best way to make rain come is to move your car that doesn't have the windows installed outside for a few days while you prep it to pass inspection, so tonight was a sprint to get the window regulators, windows, and rails back in the car before the rain came. Just started to sprinkle, not as I was finishing, but at least right as I got to the point that I could get the windows up. There's still a lot of bolts to tighten down and things to align.

Of course it won't rain QUITE hard enough to wash the car, which desperately needs it, so I'll still have that to do as well. It'll rain just enough to make it miserable to work.

Oh, the electric pump I had, and the fuel pressure regulator were both inexpensive ones that I grabbed at OReilly - so it's a piece of anodized, feels like plastic, pancake regulator that I wouldn't trust as far as I can throw it. The pump I replaced it with is a much higher quality build than the one I took off - I still have it, so if worse comes to worse I can use it to get past inspection. It's just quite loud and I'd prefer not to mess with it if I don't have to.
 

George_H

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This sounds like it could be a cracked fuel line near the tank sucking air to me. I have had the same problem. The line somehow lets air in but does not leak fuel(yet).
 
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Richter12x2

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This sounds like it could be a cracked fuel line near the tank sucking air to me. I have had the same problem. The line somehow lets air in but does not leak fuel(yet).

I'll look again, but I replaced all the fuel lines with stainless steel - there's a couple of hose connections by the rear wheel where the fuel pump was, and then at the fuel pump, but that's pretty much it. They're all clamped on pretty tight
 

dklawson

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Also look at the tank vent line and make sure something like a mud dauber hasn't plugged it. If the vent is plugged the engine can run for a while until the vacuum in the tank reaches the limit of how hard the pump can suck... then the engine dies.
 
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Richter12x2

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After running through all the things to check (floats are correct with 1mm - it's hard to tell just perfectly with them still on the car, but I can't imagine 1mm is enough to make or break it.) The fuel valves work fine, when I went to crank the engine with the float bowls off, no fuel. Pump it by hand and I get a pretty good squirt. Crank and crank and crank - nothing.

So apparently the mechanical fuel pump isn't making good enough contact with the cam to actuate the pump. I had the original fuel pump in a box, that ended up getting retired because I couldn't find or make a new seal that would last more than 3 days with the current fuel. Since the replacement pump I had bought wasn't doing the trick, I thought I'd try seeing if the seal from the top of the replacement pump just happened to be close enough to fit the seat under the glass bowl. It's not exact, but if you're careful tightening it down, it's close enough. So I swapped the seals and diaphragm from the new pump, back to the original pump that came on the car, bolted it in, turned the key, and CRACK.

Turns out the lever on there was PLENTY long enough to reach the cam, plus a bit. It broke the housing where it bolted to the engine block. That's when it struck me how new looking the base was, all the way through. Pulled it apart... it turns out apparently I'd decided that it wouldn't work before, because the base that broke turned out to be from the NEW pump. At some point I'd swapped the bases so that the lever would be the correct one that came with the engine. Popping out the diaphragm confirmed that the broken one had no stamp, and the one from the 'new' pump had AC stamped in the bottom.

So I put my old pump back together, with the good seals and diaphragm bolted it up and cranked. Nothing... okay, so maybe it needs to be primed a bit to help the seals (which I tested by sucking and blowing... just a hair of leakage when you blow the wrong way through it, probably still fine. So I primed it - nothing. Primed it all the way to the carbs, choked it and it started... ran for a while, no activity in the (now glass) fuel bowl, so I can see the nothing happening quite clearly. And the car died. Turned the key, nothing, nothing, nothing. Pumped it a few more times, started right up again.

So I ordered the Holley fuel pressure regulator, and it should be in soon, then I'll reinstall the fuel pump and insulate the heck out of it. I need to find a new place to mount the fuel pressure regulator though, because I'd like to keep the glass bowl pump in place - since it's not doing anything, it's not hurting anything - it plugs the fuel pump shaped hole in the side of the block perfectly, and looks darned cool.

Thanks for all your help!
 

trrdster2000

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Glad you are on your way to a great summer, have fun.

Wayne
 
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