Fuel Injected to Carbs

[Skyliner]

I have had several TR7's and sold them because of storage issues, but now I have a place to work on the one that I bought recently. I really like these cars. It was a project started by the previous owner. It is a 1981 that has the fuel injection parts in boxes. I had the engine rebuilt and want to put rebuilt Stromberg carbs on it, and since I have limited knowledge on this I'm going to need a lot of help. I have the carbs, intake, etc. First of all can I use the electric fuel pump that is on it. I hooked 12 volts to it but I don't hear it trying to pump. If the pump is defective can I install a mechanical one. That is what I would like to do anyway. I see that there is a plate on the right rear of the engine where one can be fitted. There are two lines coming from the fuel tank. Are both of these necessary if I use a mechanical pump? What other changes would I have to make? I'm sure I will have many more questions as this project progresses, and I'm sure some of you will recommend keeping the fuel injection system, but I'm not even sure if I have everything, and I know it can be expensive. I sure would appreciate any help you can give me.
Thanks Gary

[Paul.H]

Hi Gary, if I were you I would buy this pump https://www.summitracing.com/int/parts/ ... /overview/
They are very quiet.

Don't know what your looking at on the right rear of the block. Very early engines like the Buick 215 had a mechanical pump driven off the cam. It was mounted on the timing cover just ahead of cylinder number 1.

[FI Spyder]

Not sure why you would go backwards from fuel injection to carbs (assuming you have the parts) with all the problems associated with carbs, balancing, adjusting, rebuilding etc. My FI car had been stored for 7 years and I drove it back home 1,000 miles across an international border with no problems. I haven't had to touch it in the last ten years other than replacing the failed sealer in the gas tank ( a custom addition, not part of FI system). Other than adding injector cleaner now and again it has cost me nothing and never had a problem with it. If the PO had a problem with it he may have decided to go to carbs rather than fixing the problem? ECU's usually fail because the heavier components develop a cracked solder joint (need soldering iron), clogged injectors (from sitting with old gas) can be cleaned, worn intake tube can be repaired or replaced, connections can be cleaned.

[saabfast]

Assuming this is a 2.0 TR7, SU's are generally better than the Strombergs (may be subjective) if you want to go to carbs. Set up and balancing is not really difficult. With carbs the fuel pressure is less than with FI so the FI pump is likely to provide too much pressure (without a regulator down to 2-3psi anyway). A mechanical pump may be easier. The fuel return line is not required with carbs, just a single feed, but put an inline filter in the connection to the pump.

[Hasbeen]

Yes the mechanical fuel pump goes on the right hand side to the rear of the motor. I found it was much easier to fit a couple of studs in the block, trying to get the second bolt into the pump can be a nightmare.

The second fuel line may be the anti pollution breather, which goes from a vapour separator to a charcoal canister at the front of the engine bay. If it is, the separator will be in the compartment in the boot/trunk, with the bolt on cover.

I like SUs too, but as US cars had zenith that would be the way for you to go. More parts & knowledge available probably. Our local guru reckons there is no difference in performance either stock or high tunes between the two.

Hasbeen

[Skyliner]

I thank all you for your input. I would very much like to receive all the advice that anyone would share. I will check out the second fuel line in the morning, but I am sure it does go to a charcoal canister. Can this line be blocked off and not used at all and not have an impact on performance?
Thanks again, Gary

[Hasbeen]

No, it can not be blocked off at all, it is your fuel tank breather. US pollution gear uses a sealed fuel tank cap, & with that breather blocked off the pump will suck a vacuum in the tank, & fuel will stop flowing.

Connected to the charcoal filter it will function as your breather. If you remove the charcoal filter you could insert a small, [about 3/4"] wad of the synthetic cotton wool used in fish tank filters in the pipe to keep dirt out. Alternately you can install an in line fuel filter open to air on the end of the pipe. Neither will comply with US pollution law, but will work.

Hasbeen

[FI Spyder]

The two line fuel line on an FI is the return to the gas tank. The fuel goes from the gas tank to the pump (which is mount in front of the tank (there is a coarse screen in the pump to filter out any larger chunks (of rust or in my case sealer from getting into the pump), to the large filter (30,000 miles) which filters the fine particles from getting to the injectors, to the regulator where the line pressure is regulated down to 34 lb. for the injectors, the excess gasoline is then fed back to the gas tank to form a constant flow which is used to cool the high pressure fuel pump which would otherwise overheat. If you are converting to carbs, you would need a single pipe stopper (not sure of correct name) as the FI tank has a two hole tank and a carb tank has just one hole. On a FI set up one "stopper" has the out put and return pipe and the other "stopper" has the wiring for the gas gauge and low fuel light. Rather than trying to blank off the return line and solder it (or what ever) shut, I would get a carb "stopper" that is all in one and keep the now unused electrical "stopper" as a blank for the second hole. Or if the tank is iffy you could just buy a single hole carb tank (the two hole tanks are no longer available unless you get a custom tank built).

The FI uses the carb pump hole as a mount to support the heavy FI air plenum with stays (with an integrated blanking plate for the hole). Leaving this off will allow you to use the hole for a mechanical pump but better yet if you can adapt this support to support the carb intake and use a 2lb. pressure electric pump instead. Never seen it done but always thought it could be an elegant solution to overcome the carb rubber mounting separation problem due to their heavy weight if you are going to go from mechanical to electric pump.

[Beans]

I have a FI tank fitted to my SU powered TR7.
I just put a short piece of fuel hose with a blanking plug in to the return inlet ...

[Beans]

You can remove the emission gear but you'll need to connect the breather pipe from the tank directly to the filler neck ...



And as Hasbeen already stated you need a vented fuel filler cap.
Easy to convert a non-vented to a vented cap just drill these two holes (@ bottom of this post) ...
http://tr7beans.blogspot.nl/2010/06/dhc-report-nr-103-finishing-touches.html

[FI Spyder]

Easy fix by Beans for the extra pipe from the tank. These multiple sources of leaks always make me nervous when they sit at the bottom of things (but that's me). Beans, what did you use as the plug? Metal stock of some kind?

[Hasbeen]

Skyliner says he thinks the second line goes to the charcoal filter, so it can't be the fuel return hose.

Of course there are now many non standard minor details on my car, & most probably have a few by now, so Skyliner we can only give vague advice, as your car may be extensively modified in things like pollution control.

Hasbeen

[Beans]

... Beans, what did you use as the plug? ...

A circa 20mm long steel rod ø8mm

[Skyliner]

I thank all of you once again for all of your input. I am a little confused about the two fuel lines so tomorrow I am going to do a thorough tracing so that I will have a better understanding of them. FI SPYDER I am not familiar with the term "stopper" and would appreciate more information about what they are and do. Since I am switching to the Strombergs does anyone have any thoughts about going to a mechanical vs electric fuel pump?
Thanks, Gary

[FI Spyder]

I thank all of you once again for all of your input. I am a little confused about the two fuel lines so tomorrow I am going to do a thorough tracing so that I will have a better understanding of them. FI SPYDER I am not familiar with the term "stopper" and would appreciate more information about what they are and do. Since I am switching to the Strombergs does anyone have any thoughts about going to a mechanical vs electric fuel pump?
Thanks, Gary

I used the term "stopper" as that was what I came up with at the moment, Beans called it "blanking plug" in his picture of the two fuel lines coming and going to the fuel tank. People usually use mechanical pumps when they want to maintain originality (not the case here). As for electrical pumps, you want what I've seen called a low pressure high volume pump. The TR7/8 specialist suppliers in the States (not order takers like VB) can direct you to the brand/type they recommend. You have to be careful because there are after market pumps out there that are meant for other applications (other carburetors) that are too high in pressure. You want around 2 lbs., much higher and you will flood the carbs.