Hello,

I have a '66 122 that I am installing D-jet fuel injection into. I was all ready to get it started yesterday when I discovered that when I crank the engine, fuel is not even leaving the tank of the car.

Because the 122 was not built with a high pressure fuel injection system in mind, the tank does not have a fuel return location anywhere. What I did instead was to installed a brass 'T' in the line, before the fuel pump. That way, returning fuel would not be under pressure, and it could drain back into the tank or go to the pump. Does this make sense?

What I think is happening now is that the suction from the pump is pulling air from the return line and not fuel from the tank. The 'T' does not have any way of regulating direction of flow.

So, this is where the question comes; Is there a one-way valve sort of thing that I could install in the return path to allow fuel into the tank, but prevent the pump from pulling in air instead of gas? This seems like the easiest solution at the moment. I could also remove the tank and get a fitting installed to attach the return line to, thus separating the fuel pickup and return.

What other ideas do people have? I am surely overlooking a simpler solution. I am at a loss at the moment, really. I dearly want to get this car started.

Thanks

Hi folks,

I'll agree that the fuel pump likely won't self prime; I've been told that the pump needs to be mounted physically lower than the fuel level and then it becomes a non-issue.

I used to have a 122 that I fitted with djet; I used the same 'T fitting return line' approach that Justin describes, with the original 122 fuel tank and never had any fuel delivery problems, even below the 1/4 tank threshold. The two times I ran it out of gas, it just needed a couple gallons from a jerrycan and it always started right up again.

Justin, your T fitting approach *will* work. It's just that the Volvo Gods want you to suffer a little more. Sorry.

Best regards

I think you will find an original D jet pump is incapable of self priming. Originally they had a large dia hose and were gravity fed. I fitted a 145E tank to my 120 saloon. The original tank isn't baffled, and the car will run like a pig if the tank gets below Quarter full even if you o make it work YMMV.

Regards

I'm working on a similar FI mod. on my 67 122. I'm converting to K-Lambda on mine.

What I have done is drill and tap (and sealed with extra JB weld... thin tank material) a second fuel line close to the original one except lower. Then I used the original line as the return. On the new line, I used what is called a thermocouple fitting that allows a section of 3/8" stainless tubing to be inserted thru the fitting and in to the lowest point in the tank (which is the close to the same as the Volvo did with the original line). I used this method because I didn't want fuel supply problems caused by a low fuel level in the tank (note 240 pre-pump failures) thus keeping the inlet to the fuel pump low in the tank should eliminate any fuel feed problems and I also wanted a larger fuel line to the fuel pump. I am using a pump assy out of a K-jet 240. I then ran new plastic line, the same as new cars, to the FI filter in the engine compartment.

I haven't yet started the car. I'm running a new exhaust at the same time and the weather hasn't co-operated to get under it. But it is the same method that worked perfect on my old VW rabbit that I converted from diesel to FI.

I thought of installing the return through the top, but didn't want and additional lines and fittings sticking up in the trunk.

Good luck

Wow! That's some project!!

I went to the garage tonight and tried to plug the return to make the pump suck some gas, but still with no luck. I suspect somethings wrong with the tank itself. I have decided to take it out and get it cleaned out and get a fitting installed to put the intake at the bottom of the tank with a intake screen or something.

Thanks for the input. I'll be doing just what you suggest. Good luck with the project. Have you ever seen the article at vclassics? Lee Cordner put K-jet into a 122. Sounds like quite a ride. I'm sure yours will be, too. The article is here.

Justin;

I agree with Bill, just returning by way of a T fitting wont do it...you must return to the top of the tank...a simpler way to accomplish this might be to remove the fuel gauge sender, and strategically drill and add a brass fitting to which you plumb the fuel return( by way of a hole in the trunk and coming up from below (using metal line in the trunk)...its a bit Goldbergest, but at least you dont need to drain and pull the tank). Make certain you use the high pressure qualified fuel line for all applicable places...not just regular Gates line.

To prevent disasters, great care is advisable when working on a high pressure fuel sys!

Good luck,

Ron,

That's a good idea. Could I just route the fuel just thru the top then let it fall back down, or should I run a last foot or so of line to prevent it from splashing? Would that make it bubble? Would it matter?

THanks

Justin;

Fuel bubbles but does not foam to any extent to be a problem. In Alan's post, he mentions starvation of the pump when using the original fitting(located fairly high on the tank side...I dont know if there is a tube inside which extends into the tank and down...has anyone seen the inside of a tank and can answer this?)...this is an important point though, you may want to get some more specific info from him and do what he did (first-hand successful experience is always best!). The other idea I had (if you dont want to drill new holes into your tank...understandable, but not that big of a deal-just dont use a torch) was to use the sender flange to mount the feed tube, which could be sized such that it ended just off the tank bottom-also preventing the pump starvation he mentions (and use the existing as the return pipe).

I think that before long you'll be sucking fuel (as opposed to wind), and be up and running.

Regards,

I think you are right. the pump is just sucking air. to test it how about replacing the return line with a length of hose into a fuel can or down the gas fill port? Older fuel injection pumps used a check valve screwed into the fuel pump. Outlet was a male hose barb. inlet was something like 1/4 inch male pipe.

Bill D.