Greetings all.

Excuse my ignorance. I am new here however I searched the fourm before asking this question.

I'm in possession of a 1986 XJ6 with a Chevy 350 Small Block swap.

The small block uses a mechanical fuel pump which I have recently replaced suspecting it failed.

After replacing the pump the motor is still not getting fuel (inline filter in the engine bay is bone dry). I can extend the fuel line directly into a 5 gallon can and viola it works! The pump is doing it's job.

My question is:

I'm suspecting this is caused by either a clogged fuel line, or from my research: a faulty change over value. Is it common when the valve fails it will not drawl fuel from either tank? Is there a way to bypass this valve to text the theory, or is it common for the fuel lines at this age to clog somewhere?

Thanks for any help or direction.

 

The changeover valve doesn't have a "closed" postion. It is either "open right" or "open left". If there's fuel in either tank it should go into and out of the valve.

You could replace it with a "Y" fitting, effectively joining both tanks togehter.

As for clogs you can start disconnecting lines and seeing where fuel flow begins and ends. Do you still have the original trunk mounted filter? If so, there's one possible source for a clog.

BTW: If you disconnect any hoses at the changeover valve be prepared for a big gush of fuel

Cheers
DD

 

Thanks for the heads up with the gusing fuel! I wouldn't want that mess on my hands.

I haven't had a chance to disconnect any fuel lines in the trunk. (I'm a born Flordian and this 30 degree weather isn't shade tree mechanics friendly for us.)

As far as the truck mounted filter: Is this located toward the right side in the spare tire area toward the front of the vehicle? If so, then yes it's still there.

There is one component missing from a bracket on the right side toward the rear bumper. I assume this was the origional fuel pump location.

Also I did try to blow a small amount of compressed air though the front fuel lines, however it would no push though.

 

Yes it sounds like the "missing" piece is the old fuel pump. I would guess that the fuel lines that went to that pump are just fitted together with splice fittings now? If your fuel tanks have/had any sediment from internal rust in them it is entirely possible that a large chunk has settled into the fuel line somewhere or totally clogged up the filter.

On my car (86 as well) I put in line filters pre-pump and one coming off the line just above the frame in the engine compartment (for a total of 4) because I had sediment/rust problems. This now protects the pump and fuel rail/injectors from any of those issues. I also put in fuel tanks that were restored with Renu as more insurance.

Good luck finding the blockage, it is probably just a matter of the process of elimination on where it is.

 

Thanks for the help guys. I'll start tonight with the fuel filter and go from there.

Hopefully the filter is a ready available part from my local autoparts store if this is the issue. It's a friends car and it's stuck in my driveway until I get this figured out.

 

Here is an update on this.

I started at the back of the car and moved forward tonight. I disconnected the fuel lines in the trunk and reach one had fuel. I inspected the one way valve (ok) and blew compressed air though the lines. (also ok).

Going back to the front of the car I realized there was a leak in the supply line on the mechanical fuel pump. I'm sure it happens when I put the new one on.

Also, the reason this all started is an old friend of mine ran it out of gas. Though I replaced the pump and put a little gas in it. I'm also thinking there is either not enough fuel in the tank for the light weight pump to pull the gas to the front of the car or the pump simply isn't strong enough to prime the system.

Either way I can't do much till I get a new piece of fuel line. But I hope I'm going in the right direction. Also I'm sure the leak in the line didn't assist in building pressure.

Sorry for punctuation and spelling. Sending this from my phone.

 

Fix the line and you'll probably be OK. With a leak the pump can develop enough suction.

Heck, long before electric pumps cars were using engine mounted mechnical pumps to suck fuel all the way from the fuel tank so I doubt that your new pump is the problem

Cheers
DD

 

I have bought the filter from NAPA and Autozone. Both had them in stock. They are about $25.

 

Hard to suck through a straw with a hole in it. Same with a fuel hose, you will probably be fine once you replace that hose. Good idea to replace all the other rubber fuel hose too. If you really want to avoid trouble in the future and have long lasting hoses, use fuel injection hoses rated SAE J30R9 (printed on the hose). They will stand up to today's ethanol blended fuels for a longer time and keep your carburetor cleaner, because they have a special liner that is very resistant to fuel. Regular J30R7 hose will slowly degrade and little black bits will collect in the carb, eventually causing a clog. Fuel injection hose costs about 4 times as much for all this goodness. It's available at Autozone and other normal stores.

Good job finding the leak! Keep us posted on how it works out. And show us some pics, we're like deprived children in here waiting for new threads to appear.

 

Thanks to all of you for the help! Kudos to bbarcher for the "sucking out of a straw" comment and sneal for being spot on with the filter price. After installing the new filter I tried "repairing" the retun fuel line. No matter what I did (4 hose clamps) it kept leaking. I cut the entire house out and replaced it and it seemed to be clogged with crap and so dry rotted it easily cracked when I bent it.

I ended up finding a small slice in the fuel line that went from the main metal fuel line to the pump. Once I replaced this....viola! We have fuel appearing in the filter.

I'll try and take some pictures today. I must say, it really makes me appreciate and miss the old school way of engines. Simple to understand, cheap to repair, and everything is accessible. Makes me wish I grew up in a time before the computer controlled crap.

 

have the same setup---350 carburated in 84 XJ6-mechanical pump on block---how did you handle the fuel return line that goes back to trunk ?----did you just block it off? nice to talk on phone about this 321-274-5521---ken gosnell

 

I ran the return from the mechanical pump around the front of the block using zip ties to keep it away from anything. My return line to the tank was on the drivers side and my delivery line was on the passenger side.

 

can you give me a call---321-274-5521----

 

did you block the return inlet in trunk?--as I have fuel pouring from that if I run engine---now I can block it---if so ...wouldn't the fuel run up passenge side---and fill charcoal cannister.....does your return fill both tanks? --did you eliminate the changreover switch in trunk--and are pulling from both tanks at same time?----sure do have some questions here and can not find any of these issues on net

 

I can try to call you tonight. I was at a wedding all weekend so I'm sorry I wasn't able to get back to you. I replied from the thead on my phone sitting pool side with a cold beer.

I will call you but in short the return was still hooked up as was the duel tank setup. The only thing that was removed was the old electronic fuel pump in the trunk.