V8 fuel/overheating?

M

michael

New Member
Dear all,

I have already received good advice from Simon on the fuel pump question but I would like to float this again hoping to get some feedback on overheating or the interconnection of these problems:

Hi there,

I have a 1973 P6 3500 with similar problems which are driving me nuts because I am no great mechanic myself and have to take the car to the garage. They specialise in classic cars and seem to know a fair bit but as the fault is intermittent it is difficult to track down.

My car would run roughly after 10 miles or so (today it also felt as if it had difficulties deciding which gear was right) and then cut out. It would sometimes not restart for an hour or more (tow truck to garage: garage man turns ignition key and car starts and runs perfectly grrrrr).

This has happened twice in town traffic, and twice on low fuel going up a hill.

The distributor has been checked and the spark is fine. The fuel pump has been refurbished but there were no replacement valves in the kit.

Once when this fault occured in town traffic the temperature had shot up and today (although the temperature was shown to be in the green) I thought the radiator was nearly boiling. I opened it carefully and there was a lot of pressure and a fair bit of fluid came out.

My questions are:

Is this just one fault or is there more than one problem?

Do you think an electric fuel pump is likely to help?

Is the car just overheating? And if so what can I do to prevent that from happening?

Thanks,

michael
 
A bit of water coming out is not always because it's boiling . Hot but not too hot
I'd think it could be the coil or condenser breaking down when hot, vapour lock or a blockage in the fuel supply - try blowing through the fuel lines
Next time it stops , check for fuel flow and a spark to point you in the right direction
 
How do you know this is a fuel problem? Coil and condensor faults are very hard to find when they first start to break down, sometimes even sophisticated diagnostic equipment wont find it while they are in working state. If the ignition is definitely OK then you have a vapour lock problem or perhaps a faulty pick up in the tank. My experience is that vapour lock on the V8 is usualy heat associated so an electric pump could do the trick.
 
One way to find out is once its stopped is to pour cold water on the pump casing and then try to restart. If it starts, the pump isn't up to the job.

Also, have you checked the fuel filter? Mucky ones can really impede the flow. Take it off and just blow through it, it's been known to shift enough crud to get a few more miles out of it.
 
I had similar problems with mine.

It sounds to me like you have a slight leak in your fuel lines.

Everybody told me it would be the pump as the lines dont give trouble. however the pipe between the fuel filter and the carbs had a tiny leak which allowed air in but no fuel out so no sign of it no smell of petrol etc. I was fortunate because tis pipe was made of clear plastic so I could see the bubbles forming. I bet if you look at your fuel filter when the car has troubles that it will be full of air not fuel.

I have now got an electric pump and new copper fuel lines front to back after disabling the fuel reserve tap. But even with all these it still gave trouble until I changed that top pipe! A bit expensive really....!

I would advise that you try changing this line before you change pumps etc.

Hope this helps

Tim
 
Still have not had the time to work on the car but today I took it out of the lock-up and ran the engine and drove it a bit in circles around the lock-ups because these old cars seem to develop more faults when they are left standing.

It did take some time to get it started (guess the fuel had drained back to the tank) and it ran quite roughly on a lot of choke but after a few minutes the engine settled down into a good and smooth idle without choke.

After ten minutes I noticed the temperature creeping up to the top end of 'green'.

Any thoughts?

Does this support the theory that there is a fuel pump/vapour lock problem?

And thanks for bearing with me mechanical ineptitude.

michael
 
10 minutes running this time of year shouldn't cause it to overheat
Check for an airlock in the cooling system (the pipe between the manifold and the radiator might have blocked) or your thermostat might be sticking
 
dont necessarily worry about where the needle is too much! The guages arent that accurate.

10 minutes running will get the coolant quite hot you are best opening the bonnet and checking that both the top and bottom hoses on the rad are getting warm as well as both the smaller hoses that go through the bulk head (which will get warm first) this rules out sticking thermostats etc without taking the car apart.

If the car took a lot of cranking to get fuel up to the carbs then yes it has drained back to the tank. The only way to check this is by taking the main fuel line from the filter after the car has been stood for a while and then cranking it with the pipe in a jar. If fuel comes out straight away then fuel is not your problem.

fuel doesnt drain back to the tank if there is no way for air to get into the system. either through a knackered pump allowing air back up the return line, or through a tiny leak in that top tube!!

Good luck
 
one last thought! If the guage is accurate, then if air is being drawn in to the fuel (through a leaky fuel line) in tiny bubbles, then the engine will be running lean and hotter than it should.

My car behaved exactly like yours did re the temperature guage and it never overheated but as the guage came up you could tell when it was going to conk out!
 
OK>

I now have an electric fuel pump in the car and it ran ok today but now the exhaust is going and making such a racket that I cannot be 100% sure how smoothly.

Will need to sort that out before I can give a full report.

LOL.
 
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