misfire/loss of power under acceleration.

Mikep

Mikep

Active Member
Hi everyone,

I posted a few weeks ago regarding the poor running of my car and possible fuel starvation. I check the fuel lines were clear and upgraded my electric fuel pump to a Facet silver top and removed the fuel filters I had to solely rely on the changeable one in the filter but this didn't help. Reading some older posts I thought it best to double check my ignition as I read a faulty coil can cause a misfire. I have changed the coil and converted to Accuspark ignition (a job I've been meaning to do for ages). I readjusted the timing as it was off slightly but the car will misfire and bog down if I kick down and accelerate hard. It gets to about 50mph ok ish and then misfires quick badly and won't change up to third until I back off and let the car settle then it drives fine. No problems around town or under light acceleration. I have made sure the dashpots are topped up, which they are.

Im starting to feel like I'm chasing my tail and probably getting nowhere fast due to jumping from one thing to another but everything was fine until I suspected a faulty pump.

Any ideas?
 
Mikep said:
Im starting to feel like I'm chasing my tail and probably getting nowhere fast due to jumping from one thing to another but everything was fine until I suspected a faulty pump.
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That's probably the case. Start again at the beginning working through systematically and checking everything along the way.
 
have you checked your vacuum advance on the side of ur dizzy
I had the same symptoms and mine had failed
fitted new one now all good
cheers
paul
 
I would look at the ignition components. A friend was complaining at the weekend that his TVR chimaera was misfiring. I removed the new pattern rotor arm and replaced it with the genuine, but worn, rotor arm from my Range Rover. Low and behold, missfire gone. When comparing the two rotor arms, the metal contact on the pattern part was about half the thickness of the genuine part. Also, the pattern dizzy cap he has fitted has doesn't have the electrodes shielded where they protrude inside, so there's more chance of cross firing. The Rover V8 is very sensitive to poor ignition components, and there are a lot of poor pattern parts out there.
 
p6series1paul said:
have you checked your vacuum advance on the side of ur dizzy
I had the same symptoms and mine had failed
fitted new one now all good
cheers
paul
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Hi Paul,

This was something i suspected, it had previously been replaced though by myself in 2012 after experiencing similar symptoms. I have tried sucking it but can't make the 'points' move so I removed it and was able to just about move the arm in. Its a lot stiffer than I thought. Should this move in without any force?

Tom W said:
I would look at the ignition components. A friend was complaining at the weekend that his TVR chimaera was misfiring. I removed the new pattern rotor arm and replaced it with the genuine, but worn, rotor arm from my Range Rover. Low and behold, missfire gone. When comparing the two rotor arms, the metal contact on the pattern part was about half the thickness of the genuine part. Also, the pattern dizzy cap he has fitted has doesn't have the electrodes shielded where they protrude inside, so there's more chance of cross firing. The Rover V8 is very sensitive to poor ignition components, and there are a lot of poor pattern parts out there.
Click to expand...

Hi Tom,

I was tempted to replace at least the rotor arm as it looks genuine but couldn't say how old it is. Ive had the car for five years and the distributor is as it was when I bought the car bar a new condenser in 2012. Of course as I say I've now moved over to electronic ignition. I will have a check of the cap and see if that matches what you say.
 
My genuine rotor arm has Lucas moulded into it. The pattern part just says made in Italy, and the metal strip is held in with with a rivet. The dodgy looking dizzy cap said made in Italy too. The cap on my Range Rover is actually a britpart one, but it has the insulated terminals. The pattern parts are a lot lighter than the genuine parts.

Cheers, Tom
 
if your rotor arm is 5 years old replace it... i change the arm and cap each year on the 6 monthly oil change and it always makes it run better...
 
I've just got back from holiday so I thought I'd update on my lack of progress with getting the car running.

I replaced the rotor arm and dizzy cap before I went away but didn't notice any improvement so today, with new enthusiasm I had another look at everything. I have rechecked my timing and its sitting at 6 degrees BTDC but I still have loss of power once it gets to about 45mph and now it gradually loses power to the point of cutting out :evil:

Im totally confused by the cause. Going right back I'm sure the car was fine until I experienced a 'holed' float on the N/S carb, which I replaced and checked the float height. Since then I have:

Fitted a Facet silver top,
Checked the fuel lines are clear to the carb,
Replaced the points for an Accuspark electronic ignition,
Replaced the coil for an Accuspark sports coil,
Fitted a new rotor arm and distributer cap,
Spark plugs appear fine.

I haven't touched the carbs other than fit a new float so I'm out of ideas :( I appreciate the question is like asking 'how long is a piece of string' but I getting fed up constantly fiddling about trying to get it working right to the point where Im seriously considering moving the car on to someone who has the time to tinker and more importantly use it.
 
Mikep said:
Going right back I'm sure the car was fine until I experienced a 'holed' float on the N/S carb, which I replaced and checked the float height.
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Normally I'd say start again from the beginning, but, in view of the above, that's where I'd look first.
 
harveyp6 said:
Mikep said:
Going right back I'm sure the car was fine until I experienced a 'holed' float on the N/S carb, which I replaced and checked the float height.
Click to expand...

Normally I'd say start again from the beginning, but, in view of the above, that's where I'd look first.
Click to expand...

Thats what I have been thinking Harvey, I had rebuilt the carbs before myself and was confident about setting the float height again. I have nothing to lose by double checking.
 
A little update to my on-going saga.

Taking Harveys advice I removed the N/S carb to double check the float height after I replaced the old one. Lo and behold I had set it incorrectly by gapping it from the highest part of the float :oops: That will teach me for rushing it. Anyway having correctly set the float last night I confidently set off for a road test to find that the car is STILL misfiring and cutting out.

If I eliminate all the items I have checked and replaced I come back to fuel starvation. When I got home I removed the fuel supply pipe to the carb and turned the ignition on to see what the flow was like. Weak and sporadic are the two words that best describe it! A job I have been meaning to do is remove and clean my tank as I know that after 39 years there has some crud in there. I haven't had the opportunity to blow compressed air down the supply line from the pump but I could blow down it with ease. Therefore I'm assuming there must be a restriction straight into my electric pump at the back as the pipe into it is only six inches and new. Does this sound plausible?

Any tips on the best way to clean the tank or would it be better to get a professional to refurbish it?
 
Get one of those clear plastic inline filters and put it before the pump at the rear, you'll see how bad the problem is (in fact do this before the pump anyway). If not then perhaps the pump itself isn't great. It could be debris have damaged it. Should be easy enough to bench test.

I've never tried the epoxy sealer kits but I can tell you acid dipping and sealing I had done professionally on my old Sunbeam Alpine was a complete success. This might not be so expensive if you remove and refit the tank yourself. As it was it cost me £300 in the late 1990s. Before that, the filter would clog completely in under a mile! However It could be "reverse flushed" to get me home again.
 
PeterZRH said:
Get one of those clear plastic inline filters and put it before the pump at the rear, you'll see how bad the problem is (in fact do this before the pump anyway). If not then perhaps the pump itself isn't great. It could be debris have damaged it. Should be easy enough to bench test..
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Hi Peter, I used to have an inline filter before the old electric pump and one just before the carb. The rear one wasn't actually too bad but did have one piece of rusty metal in it! When I fitted the new pump (cant remember off hand if its a red top or silver top) I removed both inline filters to rely on the pumps integral one. My reason for this was that I was concerned about overly restricting the flow. The car hasn't run properly while the pump has been in there so I doubt its been damaged. I'm thinking that maybe the pipe out of the tank is partially blocked.
 
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