Need help with fuel issues...

[SuDZ]

first of all , pumping on the throttle has Zero effect when the engine is not running. These carbs as well as the Round top SUs have no accelerator pump like is found on American cars or Weber's. When you turn the key the electric pump should activate. The mechanical pump only works when the engine is turning over . It works off the cam in the engine. Before you start pulling things apart. Test to see if the elect pump is getting power . You could have a broken wire or a blown fuse. Check the fuses with a continuity test , don't just rely on looking at the fusible strip inside the glass. The engine will run just fine on just one pump. I am running the electric only and have been for years. I cannot remember if the 260 had a electric pump cutoff that cut power if the engine was not running , a safety measure. If any one has info in this chime in here. Gary

I had a feeling I was accomplishing nothing on pumping the pedal. I must admit that my only experience with carbs was pretty much on US cars. Glad to know that now though and I don't use that as a gauge to tell what may or may not be working.

I was figuring I can remove the elec pump tonight and see if I can hook it up to a 12v source and see if I get any action off of it. I am figuring I will at least hear a click of some sort or it trying to work as well as replace the filter and see what was inside. I will take your advice on checking out the connectors and fuses as well.

Thanks for the help.

SuDZ

[SuDZ]

i replaced my stock electric fuel pump with the 12vt Holley offered by MSA. when we first turned the key on, it wouldn't run. this car had been sitting for the last twenty years. taking a pair of jumper cables, we attached them directly to the pump off of the battery and it ran fine. after a few minutes, the pump ran on its own. my buddy helping me figured that the relays had finally kicked in, getting power to the pump after sitting for so long without working. we have had no problems with the pump since, and even did away with the mechanical pump on the engine. fwiw

butch

I had seen that pump also when I was cruising the MSA site. Is the benefit of the new pump just the fact that it's newer or does it actually perform better somehow? If it doesn't need to be replaced just yet I will hold off. I guess testing it tonight will let me knows whats what.

SuDZ

[Mat M]

The intake tube in your tank may be corroded/varnished/rusted solid after sitting so long. I just found this to be the case with my car. Some days it runs, other times it doesn't. it took me three different electric fuel pumps to get mad enough to drop the tank and blow air through every line the gas could possibly go through. Finally, it ended up being the intake tube, which, on a 71 tank, does not lend itself to removal/cleaning very easily. I used a copper solid core (10 gage) wire and a can of carb cleaner with a straw to ungunk the less than 10 inch tube.

Next for me: Radiator shop to boil the tank, then POR-15!!!

[SuDZ]

The intake tube in your tank may be corroded/varnished/rusted solid after sitting so long. I just found this to be the case with my car. Some days it runs, other times it doesn't. it took me three different electric fuel pumps to get mad enough to drop the tank and blow air through every line the gas could possibly go through. Finally, it ended up being the intake tube, which, on a 71 tank, does not lend itself to removal/cleaning very easily. I used a copper solid core (10 gage) wire and a can of carb cleaner with a straw to ungunk the less than 10 inch tube.

Next for me: Radiator shop to boil the tank, then POR-15!!!

The part that has me wondering though is the fact that even when I take fuel and put it directly into the fuel inlet tube, I still can't get it to turn over.

Last night I took apart the elec fuel pump and it had a pretty worn filter in it. I was looking to replace that but it seems that it may be dead all together since I couldn't get it to activate at all on a bench test.

I blew air through all my lines and everything looked clear and fine. The thing that bothers me is that even with the gas directly going into the carbs I wasn't able to get it to turn either.

I'm kind of stumped.

SuDZ

[Mat M]

...Snip... The thing that bothers me is that even with the gas directly going into the carbs I wasn't able to get it to turn either.

I'm kind of stumped.

SuDZ

Now I am, too. I am assuming you have checked all the easy things, like float level, and the proper functioning of the needle valve (is that the correct term?) that is in contact with the float, as well as the proper oil in the domes. And the not-so-easy things like needle seat depth?

[SuDZ]

Now I am, too. I am assuming you have checked all the easy things, like float level, and the proper functioning of the needle valve (is that the correct term?) that is in contact with the float, as well as the proper oil in the domes. And the not-so-easy things like needle seat depth?

That's my next step. I will have to remove the crabs to inspect all that. Last night after messing with all the fuel lines for so long I gave up on it for the night. I am hoping to get more time out there tonight to check everything out though. I do know though that the oil is right in the domes but will have to check the floats next.

SuDZ

[beandip]

SuDZ, Since you are running flat top carburetors some of the suggestions given may not apply to you, if they are unaware of this. 90% of carbed Z are running SUs ''round top'' and they are a totally different animal. If you blow air into the tank through the supply hose is it clear? A inexpensive replacement for your electric pump , that is if you want to buy one at a Bone yard. Is a pump from a RX-7 that is not injected. I have been running one for years out of a '80 RX-7 and recently bought a spare , $15.00. They are quiet and you wont even hear them run when the engine is running. If you need to clean the fuel line coming out of the gas tank or any where else , you can use an old speedometer cable on a drill . It will work like a roto-ruter and loosen any crud. Then you will need to flush the line. Just be careful working around gasoline especially if your drill is a plug in type . If you are only finding varnish in the lines , this will dissolve with time and use. Unless it is vary severe. Have you tried spraying starting fluid in the intake of the air cleaner when attempting to start the engine? Gary

[beandip]

Just how many years has this Z been sitting with our being run? I just reread the complete thread and didn't find this info. You did say that the carbs were rebuilt. Has the engine been run since they were installed? Did you do the rebuild or a mechanic? Try the starting fluid in the inlet of the air cleaner before you start messing with the carbs. The engine should try and start with the use of the spray. If not you have other issues. You mentioned the 400 RPM figure on the mechanical fuel pump. They pump immediately when the engine turns over on the starter. I works off the cam and is a simple lever that in pushed up and down by the cam as it rotates . It moves a rubber diaphragm up and down and pumps the gas. It takes a while to draw fuel all the way from the tank when the lines are empty. These pumps can fail and push gas into the engine diluting the oil, or spray gas down on the alternator. Either place is not that good. Vary old technology. Gary

[SuDZ]

Just how many years has this Z been sitting with our being run? I just reread the complete thread and didn't find this info. You did say that the carbs were rebuilt. Has the engine been run since they were installed? Did you do the rebuild or a mechanic? Try the starting fluid in the inlet of the air cleaner before you start messing with the carbs. The engine should try and start with the use of the spray. If not you have other issues. You mentioned the 400 RPM figure on the mechanical fuel pump. They pump immediately when the engine turns over on the starter. I works off the cam and is a simple lever that in pushed up and down by the cam as it rotates . It moves a rubber diaphragm up and down and pumps the gas. It takes a while to draw fuel all the way from the tank when the lines are empty. These pumps can fail and push gas into the engine diluting the oil, or spray gas down on the alternator. Either place is not that good. Vary old technology. Gary

The Z has not been run in about three years. I had the carbs rebuilt by a carb shop around my area about two - two and a half years ago or so.

I am going to pick up a can of the fluid tonight since I ran out and only had a couple sprays worth in the can at my house. I am going to see if this gets me someplace.

I had read in the Haynes manual that the pump doesn't start until the 400RPM mark. This was for the elec pump though, not the mechanical one.

I am going to keep playing around with it though and see where I can get.

Thank you so much for the help so far.

SuDZ

[Mat M]

Beandip, you may be on to something. IF you are getting fuel at the bowls, then the mech. pump is working. SuDZ, you haven't mentioned if your float bowls had gas.

If it were me, I would tear down the pump for an interior inspection. Easy to do, and easy to put back together!

[Mat M]

STUPID 5 MINUTE EDIT RULE!

I meant, if you didn't have fuel at the bowls after a while of cranking the motor, then you would be right to suspect the mech. F.P.

[Nigel1943]

If I'm reading this right you've got two pumps in the system which seems a bit crazy to me. When you switch on the ignition the electric pump will be trying to push fuel to the mechanical pump which will block the fuel until the engine is running. Try bypassing the mechanical pump after making sure the electric one is working. With the ignition on leave an open end on the fuel pipe (in the engine bay) until fuel is pumped thro, connect to the carbs and hopefully you'll get fuel to them as well.