Still problems AFTER rolling rd

[chr15w]

Originally Posted by Neil O

If it coughs and backfires, surely it's more likely to be ignition rather than fuel starvation.
I had fuel starvation on my Dax once, and the engine would just die off. Unburnt fuel in the exhausts would be the backfire wouldn't it?

Dizzy module problem perhaps?

That makes sense but how can I check?

[Neil O]

Rolling road with a fuel pressure gauge would rule out fuel starvation I would think. An easier way would be to measure the amount of fuel the pump pushes and check if it is enough for full chat. There's another thread running currently with a similar theme.
Maybe get a new dizzy module and swap it over? I don't know anything about the Luminition set up, so maybe, someone cleverer than me will be along shortly.........
I supose your HT leads could be breaking down?

[craggle]

Had fuel starvation on an old Range Rover once that would only show itself when towing a heavy trailer up hills.
It would cough, spit, backfire and generally not run well until the load was reduced or the revs dropped.
Spent a fortune changing coils, distributors, plugs, leads Etc. until someone suggested fuel starvation. I was skeptical but found a blocked pickup pipe in the tank itself. Cleaned this and changed the filter and it ran perfectly thereafter.

If you have a filter before the pump (which you should have) change or clean this. If you don't have a filter before the pump remove the pump and check the internal filter then fit a pre-pump filter.
The Facet red-top pump is sufficient for the Rover 3.5 V8. If it's one of the small, square, solid state Facet pumps I don't think they are up to the job.

Craig.

[snakebite]

Is your coil mounted vertically?

[chr15w]

Originally Posted by snakebite

Is your coil mounted vertically?

Yes it is vertical

[mikey]

If you had gone for a rolling road analysis then you should have had a crypton, Sun or similar unit hooked up. This would pick up any coil or ignition lead issues etc and even bounce on the dwell would be obvious on the trace setting.

Plugs can obviously be checked even if it means changing them.

Temperature hook up and hydrocarbons monitors will establish if there is a serious misfire condition although they may not have the equipment to detect temperature using your headers at each exhaust port.

Point is that if the condition is an electrical one this should easily be pinpointed if the guy knows how to use his equipment. If not, if the misfire is specific to certain cylinders you can normally detect it as if the engine is out of balance, unfortunatel coil breakdown is not as easily detected but shows up readily on the crypton. If its a fuel power problem, see if you can borrow a carb to bolt on to try, it will show you immediately if the problem is there.

I really am stunned at how many posts we have where given the equipment and a rolling road, the results are that trial and error methods are adopted by the operators or simply you have a problem sir comes out. It gives little confidence on the establishments using rolling roads and a bad reputation for those that may actually be able to use them.

As a first step I would ask for the readouts of the electrical system on the firing side (if they were done) and post them so we can look at them. Trace at the leads would be useful as it will determine if it is electrical and if it is cylinder specific.

Also check the resistance of the plug leads and post this. I can't remember what they are supposed to be, but I am sure Wilf will tell you off the top of his head.

Final but obvious one is check the distributor cap for cracking. This can cause poor starting and arking at high revs. I guess you ar enot using a points condenser system as again if you are first visit is change the condensor as its a bit like rolled up silver paper and if it goes can mimick all sorts of engine problems as it stops doing its smoothing out role.

Mike

Mike

[Sidecarbod]

From what I gether from the first post the engine is OK above 2700 rpm. If this is the case then I don't think it can be a fuel delivery issue because it would get even worse as the revs went higher. The problem with some rolling roads is that they only load the engine up in an acceleration "mode" in the real world the load on the engine is more or less constent and high at high speeds. Therefore you need to test the engine on the road at higher revs than 2700. If it plays up then yes it could be a fuel stavation issue, if its OK then this can not be the problem. (well not at 2700, it could be a problem at higher revs!)

The formula that I posted up on the other thread may help.

(Fuel in CC/minute) = 4.6 x BHP

You can guess your BHP to be round 155 for a standardish lump up to 230 for a hot lump. Let your pump fill a container for one minute then measure in CC the amount that it has pumped. 1058 cc will make 230BHP. Really you want it to be able to pump more than that. My pump will deliver 2000 cc. I would be worried if I was you if it was less than 1500 cc. This test does not check the PSI pressure, just the amount of fuel being delivered. (They are two separate things).

You should also check things like your static timing, the bob weights and springs, the vac advance etc. (2700 could be around the point where the bob weights are fully advanced, if something funny is going on with them it could cause your issue).

I don't know anything about Holley carbs but it could be going lean. Does the problem change if you open or close the throttle slightly?

Regards,

Pete

[chr15w]

Originally Posted by mikey

If you had gone for a rolling road analysis then you should have had a crypton, Sun or similar unit hooked up. This would pick up any coil or ignition lead issues etc and even bounce on the dwell would be obvious on the trace setting.

Plugs can obviously be checked even if it means changing them.

Temperature hook up and hydrocarbons monitors will establish if there is a serious misfire condition although they may not have the equipment to detect temperature using your headers at each exhaust port.

Point is that if the condition is an electrical one this should easily be pinpointed if the guy knows how to use his equipment. If not, if the misfire is specific to certain cylinders you can normally detect it as if the engine is out of balance, unfortunatel coil breakdown is not as easily detected but shows up readily on the crypton. If its a fuel power problem, see if you can borrow a carb to bolt on to try, it will show you immediately if the problem is there.

I really am stunned at how many posts we have where given the equipment and a rolling road, the results are that trial and error methods are adopted by the operators or simply you have a problem sir comes out. It gives little confidence on the establishments using rolling roads and a bad reputation for those that may actually be able to use them.

As a first step I would ask for the readouts of the electrical system on the firing side (if they were done) and post them so we can look at them. Trace at the leads would be useful as it will determine if it is electrical and if it is cylinder specific.

Also check the resistance of the plug leads and post this. I can't remember what they are supposed to be, but I am sure Wilf will tell you off the top of his head.

Final but obvious one is check the distributor cap for cracking. This can cause poor starting and arking at high revs. I guess you ar enot using a points condenser system as again if you are first visit is change the condensor as its a bit like rolled up silver paper and if it goes can mimick all sorts of engine problems as it stops doing its smoothing out role.

Mike

Mike

When I took the car to the RR (rolloing road) I assumed it would be the answer to all my prayers, alas no. Im sure the engine is running as efficiently as it is possible but I naively assumed all the points you raised would be checked as such I only received a bhp/torque chart, I didnt think to ask for anything else

Originally Posted by Sidecarbod

From what I gether from the first post the engine is OK above 2700 rpm. If this is the case then I don't think it can be a fuel delivery issue because it would get even worse as the revs went higher. The problem with some rolling roads is that they only load the engine up in an acceleration "mode" in the real world the load on the engine is more or less constent and high at high speeds. Therefore you need to test the engine on the road at higher revs than 2700. If it plays up then yes it could be a fuel stavation issue, if its OK then this can not be the problem. (well not at 2700, it could be a problem at higher revs!)

The formula that I posted up on the other thread may help.

(Fuel in CC/minute) = 4.6 x BHP

You can guess your BHP to be round 155 for a standardish lump up to 230 for a hot lump. Let your pump fill a container for one minute then measure in CC the amount that it has pumped. 1058 cc will make 230BHP. Really you want it to be able to pump more than that. My pump will deliver 2000 cc. I would be worried if I was you if it was less than 1500 cc. This test does not check the PSI pressure, just the amount of fuel being delivered. (They are two separate things).

You should also check things like your static timing, the bob weights and springs, the vac advance etc. (2700 could be around the point where the bob weights are fully advanced, if something funny is going on with them it could cause your issue).

I don't know anything about Holley carbs but it could be going lean. Does the problem change if you open or close the throttle slightly?

Regards,

Pete

The engine will accelerate well to all revs in 1st - 3rd but on Mway it doesnt like to rev above about 2700 in 4th & 5th

I have just changed the Filter king for a straight through filter by way of a test, when the weather stops raining Ill try it and see if I have any improvement

[mikey]

Originally Posted by chr15w

When I took the car to the RR (rolloing road) I assumed it would be the answer to all my prayers, alas no. Im sure the engine is running as efficiently as it is possible but I naively assumed all the points you raised would be checked as such I only received a bhp/torque chart, I didnt think to ask for anything else





The engine will accelerate well to all revs in 1st - 3rd but on Mway it doesnt like to rev above about 2700 in 4th & 5th

I have just changed the Filter king for a straight through filter by way of a test, when the weather stops raining Ill try it and see if I have any improvement

You sound guilty about not being able to ask what you need to sort it out - dont be, the point is that having found something they should be advising you.

Are you going to Hraewood show or Harrogate show as I will be more than happy to try and help if I can. Also do you have a local meet. If so just bolt on one of your fellow member carbs and try it out. If its a big improvement just carry on driving home, you can always say you forgot.

Mike

[Purple AK]

The first thing I would do before anything else is check the flow rate of the pump (as Pete and others have suggested) Quite simple, just pull the fuel hose off the carb and with an extension hose, see how long it takes to fill a 5lt petrol can. Is the Facet pump square or round? The square solid state ones don't deliver enough flow for a Rover to begin with. But if it's a Redtop (round) it should be sufficient, but it could have a split diaphram especially if it is aged. Or a blockage that is restricting the flow.
Do this simple check and come back with the result before we throw anymore wild guesses into the hat!
I had a similar senario and spent £100's of pounds changing and upgrading the ignition system!! Before finally doing the above, only to discover a blockage in the pump filter which was restricting the flow