No More Speed After 4000RPM

[Pilot25dmc]

Hi folks

Well my problems seem to be continuing....

Took the car out today and onto the motorway, car went well in 3rd up to say about 55mph and 4000rpm, then it stopped accelerating and bogged down with a dramatic change in exhaust tone! it just would not rev any higher than 4000rpm, I changed into 4th and the car accelerated up to about 70mph but once it hit 4000rpm it stopped accelerating again and bogged down..... in 5th it just sits at about 70mph and wont go any higher.

I have new injectors, metering head, WUR, Fuel pump relay, fuel lines.... all of these have been fitted in the last 6 months. Car ran fine before I fitted the new metering head, fuel lines and new fuel pump relay (its the green one), I stuck in £25 of fresh petrol to see if that helped but it didnt make any difference.

I have never had this problem before and had thought it was a mixture problem but I have the car set to 2.5% and it drives PERFECTLY untill it gets to 4000rpm.

I doubt its the clutch as the revs dont increase while the speed stays the same and I have driven a car with a slipping clutch so it nots that, I expect its either the fuel pump or the fuel pump relay but I would love some advice before I start ripping things apart.

The car starts first turn of the key when cold and when hot.

P.S. The car will go higher than 4000rpm in 1st and 2nd, its just 3rd and 4th where I have a problem, although you can feel the car starting to bogg down in 2nd when you get to about 5000rpm

Please! Has anyone any idea!!!!!!?????

[Pilot25dmc]

I richened the mixture slightly and it seemed to help slightly, I can now get to about 5000rpm before the problem occurs.

I am now thinking my rebuilt metering head is causing the problem, my mixture used to be spot on at 2.5% but my new metering head has been a real pain to get set right.

I might put my old one back on and see if it makes a difference.

[Dan6457]

Have you got the new O2 sensor fitted now?

[Pilot25dmc]

I tested the old one ands it working fine, the whole lamda system is working as it should. I either have the car too lean (which I really really doubt) or my new rebuilt metering head is crap. I am going to change back to my old metering head tonight and see if that helps any, there wasn't anything wrong with the old one but I changed it because I thought it would make a difference, well it did, the car drives like crap!

[stunned_monkey]

revvy probs tend to be ignition related, although get hat new lambda sensor in first to rule that out.

Check simple stuff first like connections on your ballast resistor and coil. Have you got a spare coil you could try?

Prettymuch all other ignitin possibilities are inside the dizzy itself - either the pickup coil or a problem with the advance weights. I had one car that wouldn't rev past 4000 and it turned out to be a snapped spring on the secondary advance weight. That's a rare one though.

[steve.s]

hi

i think its the old saying

if it ain't broken, don't fix it.

if it runs fine on the old head, sell the new one!.

[Pilot25dmc]

I am now thinking that it is fuel related, it is either the fuel filter or the pump.

The car is perfect at all other times, its starts on the button when cold and when hot, it will idle all day long at 1000rpm. It is only when I drive onto a road that has a speed limit over 50 that I have a problem, thats when the fuel pump is running at its optimal pumping speed, if there was a problem here then the pump would not be giving enough fuel to the engine and it would be starved giving me the bogged down effect that I am experiencing. I am going to rip out the pump tonight and see if either the baffel is loose or the filter screen is ripped or even missing, I have Special T Autos updated baffel kit so I dont have a pickup pipe, I have well over 3/4 of a tank of fuel so I am not sucking air when all the fuel rushes to the back of the tank when I accelerate.

I will do this first and if that does not help, I will change the filter, if that still does not help then I will change the coil and the plugs.

It will end up being something stupid, I know it.....

[stunned_monkey]

Hi Al, if the pickup filter is blocked, the pump usually makes one hell of a noise. I've yet to see a pump fail without just simply conking out. They either work or they don't. I have seen a blocked flter cause the problems you're describing.

Can you swap back your original metering head? It was the last thing you did... the primary pressure could be set up wrong.

I don't think it'll be plugs.

[Pilot25dmc]

Your the second person to suggest that Martin, I might just do it seeing as its sitting in a box in my garage.

It was a rebuilt unit from Ed Uding and I already sent one back because it was leaking, this is the second one.

If the primary pressure is set-up wrong what can happen?? If you tell me I can see if similar things are happening to me.

[stunned_monkey]

the fuelling is basically a straight line graph, fuel against air. the more air, the more fuel... the primary pressure sets the "steepness" of the line. It could be too rich or too lean, either way it will get to a point at higher load where the lambda system can no longer compensate for the discrepancy.

I'd be surprised if the primary regulator was set wrong though. However the copper washer that seals the regulator can make a massive difference if it's changed for a thicker one (will lean it off) or thinner (will richen up)

[Pilot25dmc]

I removed the new metering head last night and replace it with my old one, I have not had a chance to test it yet as I am still waiting on my new o2 sensor.

I removed the control pressure regulator to check it and the washer that you where talking about looks really old and rusty, I dont think it was changed when the metering head was rebuilt. I have also got a new fuel filter which I will throw on tonight. All being well I can give her a quick test on Thursday evening.

I am sort of glad it happened now and not a week before Eurotec or even on the way to Eurotec, gives me enough time to sort out the problem and fit the new parts.

I will let you know what happens.

[bozzzydmc]

Pilot25dmc Wrote:I removed the new metering head last night and replace it with my old one, I have not had a chance to test it yet as I am still waiting on my new o2 sensor.

I removed the control pressure regulator to check it and the washer that you where talking about looks really old and rusty, I dont think it was changed when the metering head was rebuilt. I have also got a new fuel filter which I will throw on tonight. All being well I can give her a quick test on Thursday evening.

I am sort of glad it happened now and not a week before Eurotec or even on the way to Eurotec, gives me enough time to sort out the problem and fit the new parts.

I will let you know what happens.

Fingers crossed on the metering head bud

[NickT]

Try linking out the fuel pump relay first:



This will ensure that the fuel pump relay can be ruled out.

I would test for correct fuel pressures next.
If you don't have a fuel pressure gauge then just swap the fuel distributor over.
I am presuming that the reconditioned one you got is of the same part number etc.

Good luck.

NickT

[steve.s]

i forgive me if i am wrong, but the pump rate of fuel is constant from the fuel pump.

its either on or off.

have you considred a collapsing fuel pick up pipe? and poor in tank filter.

[Pilot25dmc]

I have this kit from John Hervey



There is no pick-up pipe to get kinked or risk of collapse.

Some say that it can be a problem when the car is low on fuel and you either accelerate to hard or try to drive up a hill, all the fuel rushes to the back of the tank and the pump then sucks in air. I have never had this problem, 1 reason being I never let the car get below a 1/4 of a tank so the fuel is never low enough for this to happen in the first place.

I fitted a new RPM relay about 3 weeks ago, I have a spare one which I can fit if all the other things dont work.

I removed the fuel filter last night and have already got the old metering head back in the car. Still waiting on stupid Fedex to deliver my o2 sensor, noticed on their tracking page that my parcel that was supposed to be delivered on the 10th of March now says "unavailable to quote delivery date", 3 days shipping my arse.