Ignition trouble

MCBladeRun

Club Member
Hi guys

Tried starting the car today and the starter motor could turn the engine over, but the moment I take it out of start and into run on the ignition barrel - it dies.

I started to think it could be an earthing problem and I started to read up on possible issues with the electrics, checked the LT and HT leads were in, and had a look at the dizzy cap etc (not that I would know if there was a problem).

Then I remembered I replaced the fuel filter and I think I'm starving my engine of fuel.
I couldn't find any how to or whatnot on the subject of purging or cleaning the fuel lines or where to start checking?

What I'm asking is, if you guys suspect it of a blockage in the fuel line, how do you go about clearing the blockage? I know not to use plastic to contain fuel from experience..

Should I just start undoing pipework one at a time and emptying it out, blow some air from a can through or something?

Any advice would be appreciated thanks.

Martin
 

jonbills

Membership Secretary
Site Administrator
what kind of car is it? on 240/260 at least there's two supply wires to the coil, one either end or the ballast resistor. 12v for start and 8v for run. Knock the run one off and it'll start but not run.
 

MCBladeRun

Club Member
what kind of car is it? on 240/260 at least there's two supply wires to the coil, one either end or the ballast resistor. 12v for start and 8v for run. Knock the run one off and it'll start but not run.
Yeah my bad, it's a 240z with a 2.8l engine.
It has both the resistor and coil.

I saw the 3 wires to the coil, one on the +ve and two on the -ve. The -ve I noticed isn't earthed?

Do you think I should continuity check the 8v run wire you mentioned?
 

jonbills

Membership Secretary
Site Administrator
how about the wires to the ballast resistor? there should be 3 - 2 supply from the loom and 1 to the coil.

the coil -ve goes to the distributor which controls the coil dwell and discharge.
 

jonbills

Membership Secretary
Site Administrator
also, not clear from your first post if it fires when cranking, or just cranks. can you confirm?
 

jonbills

Membership Secretary
Site Administrator
Just cranks, doesn't fire, hence why I thought fuel issue
Yes, sorry, ignition possibly a red herring then [emoji16]
Where's the fuel filter? in the engine bay? I'd probably disconnect the fuel line at the engine and see if there's fuel coming there and work my way back.
 

MCBladeRun

Club Member
Yes, sorry, ignition possibly a red herring then [emoji16]
Where's the fuel filter? in the engine bay? I'd probably disconnect the fuel line at the engine and see if there's fuel coming there and work my way back.
No worries Jon, just happy to have help :)

I get that I can disconnect the fuel line, but if I start at the engine and work backwards, i guess I'm just looking for where there is no fuel - because of a blockage presumably? I may need a glass jar for spillage..

Fuel filter is in the engine bay yes.
 

jonbills

Membership Secretary
Site Administrator
yes thats right. are you on carbs with a mechanical fuel pump?
obvs if electric pump, check its running.
isn't the fuel filter clear?
 

MCBladeRun

Club Member
yes thats right. are you on carbs with a mechanical fuel pump?
obvs if electric pump, check its running.
isn't the fuel filter clear?
Yes, twin SU round tops with mechanical fuel pump. New fuel filter is clear and I can see fuel in there
 

jonbills

Membership Secretary
Site Administrator
Yes, twin SU round tops with mechanical fuel pump. New fuel filter is clear and I can see fuel in there
Ok, I'd disconnect the hose from one of the carbs and crank it. if there's fuel I'd go back to checking for sparks. if there's no fuel, can you suck fuel from the line to the pump?

I have a vague recollection filters might be directional - is it on the right way round? (I mihhttbr imagining that though!)
 

SacCyclone

Club Member
First, push up on the main jets under each SU to make sure they did not stick open.
Second, spray some start fluid in the SU's and see if it lights......if yes then its probably a fuel problem....if no then if may be electrical.
Also, the ignition switchs are known to go bad if the contacts fall apart or corrosion is present.....you may have to bypass switch to see if thats a problem.
Mike
 

Bazzateer

Club Member
Ok, I'd disconnect the hose from one of the carbs and crank it. if there's fuel I'd go back to checking for sparks. if there's no fuel, can you suck fuel from the line to the pump?

I have a vague recollection filters might be directional - is it on the right way round? (I mihhttbr imagining that though!)
You're right, they are usually directional and most have an arrow embossed to show direction of flow.
 

Bazzateer

Club Member
Also, the ignition switchs are known to go bad if the contacts fall apart or corrosion is present.....you may have to bypass switch to see if thats a problem.
This happened on my Mum's 76 Colt Galant. Twisted the key, it turned over then caught and ran, but as soon as you release the key it cut out. A solder joint on the ign switch had failed.
 

Farmer42

Club Member
My first thoughts are that your float valves have stuck. Had the same problem recently and a tap on the top on each carb freed them to allow fuel through. Take the float lid off and see the chamber has fuel in it if not the valve has stuck closed. It only takes a little bit of debris to clog it and it could have been dislodged when you changed your filter as I did.
 

johnymd

Club Member
I'm still a little confused as to what is actually happening. It's best to know the conditions as they will lead to the answer.

You say it dies when going from cranking to run therefore it must of been alive (running) at cranking. Is this true or not? You also mention continuity but with what?, as Jon asked but you didnt answer. What are you actually test here? If you can clarify these points then it will help us suggest the next things to look for. Old cars are very very simple but to fault find you have to be logical and systematic in your approach rather that flitting from one thing to the next. Ruling out things is the only way forward as Mike mentioned with spraying a flammable liquid into the carbs to see if it fires. That simple thing could rule out the entire electrical system as a reason not to run.
 

MCBladeRun

Club Member
Okay, so just taken another look at the car.

It cranks on ignition and the engine runs /turns in that position, but as soon as you let go of the key into 'run' mode, it instantly stops running.

I've checked the voltages I've got on the resistor and the ignition coil and I've got 11v on every terminal to earth (this is with the key in 'run' position).

I've also looked at the floats adjacent to the carbs and they've got fuel in them. I took apart the ignition switch, and had continuity where I was supposed to in different switch positions - I can't be sure if it's a solder joint as I couldn't dismantle it further without causing more problems.

I followed what Saccy said, bought some starter spray and applied it, started the engine and it was the same result. So, I'm starting to doubt it's a fuel issue now, as even when it turns over on ignition, it smells of burnt fuel out the exhaust like usual.. I've yet to try bypassing the ignition switch as, I've no idea how to do that (yet).

So that's where I am with it. I got frustrated the other day, so started continuity checking the wires to make sure there were no breaks in the them.
 
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