robbh

robbh

Crazier than a box of frogs on acid
Hi all.

I know this subject has probably been done to death but seems no matter what i try i can't get my V8 to rev :mad:

Also my first V8 so it's all a bit confusing :eek:

Right to start off i bought the engine from Dr Evil and it was running fine in his series. He removed it and shipped it down to me. Have since fitted it to my series and now can get it started but won't rev. It just splutters and dies.

So far I've played with dizzy timing, checked all connections, checked vac pipes, checked all points on ht leads, and now at a lose as to what to do next. Everything appears to be fine.

So far have been able to get the revs to increase slightly by slowly pressing the throttle but gets to a certain point and dies.

Please help.
 
The fuel delivery system was not common to the engine when it was running in Doc's motor. Maybe it's a funky fuel pump or clogged filter. I'd start there.
 
You running efi or carbs? If efi is it flapper or hot wire?

Could be fuel pump or inlet air leak. EFI won't run on a fuel pump for carbs - pressure too low. If EFI, check throttle potentiometer. HTH
 
West Slope Rover said:
The fuel delivery system was not common to the engine when it was running in Doc's motor. Maybe it's a funky fuel pump or clogged filter. I'd start there.
Click to expand...

I'm currently running a fuel pump half way up the fuel line. It's a high pressure one but not sure if it's doing it job tbh. I do have a fuel pump from a 3.9efi discoverys fuel tank that i will retrofit inside the tank to see if it makes any difference.

classic kev said:
You running efi or carbs? If efi is it flapper or hot wire?

Could be fuel pump or inlet air leak. EFI won't run on a fuel pump for carbs - pressure too low. If EFI, check throttle potentiometer. HTH
Click to expand...

EFI flapper. Will check pententiometer if the new fuel pump doesn't do the trick.

Thanks for the advice so far guys. I will report back once I've connected up the disco fuel pump and let you know how i get on. :)
 
robbh said:
I'm currently running a fuel pump half way up the fuel line. It's a high pressure one but not sure if it's doing it job tbh.. :)
Click to expand...

Most high pressure pumps are good pushers but not good suckers(!) I had to have a standard facet pump to get the fuel out of the tank and up to the other pump.

Is your fuel return pipe connected?
 
Small update on this.

Fitted the discovery fuel pump inside the tank and has made no difference whatsoever :(

Still can't get it to rev.

I have another pententiometer from a 3.9 efi I could try to see if that makes any difference.

If not will just go through everything until i find the problem :(
 
Ahh yes, Flapper EFI! I believe the saying is "test don't guess". Now before you go and disturb too much, stop! Also you don't want to start replacing things left right and centre, that can get expensive and you also might end up replacing perfectly good things! :(

Might I point you towards this:

3.5 V8 Flapper system Diagnostic Manual

If you haven't got those two PDFs already, then download them! I've attached them to this post as well, just in case you haven't registered. The two PDFs attached are excellent reading material and cover almost everything!


Now, before you go probing and blaming the EFI system, I've read that youve "played with dizzy timing, checked all connections, checked vac pipes, checked all points on ht leads"

It sounds unlikely that the EFI side would suddenly die through a transplant, possibly timing or air getting in. I don't know as its not in front of me. :) So you've played with the timing, but is the timing actually correct? Do you have a timing light to check? Just make sure the ignition side is okay before you start blaming the EFI. If it idles fine, you rev it and then it dies, are you sure all the pipes are in good condition and not letting any air in? Any unused inlets are covered? etc etc. Make sure everything else is spot on before you blame EFI!

Once you do get down to testing the Flapper EFI, then make sure you go through the list as well:

GENUINE Dizzy and Rotor Arm
Decent Leads - not much beats a Genuine set to be honest
NGK BP6RES PLugs NOT Champion esp
Timing light check, does it advance also when you rev up
Coil - NOT an Intermotor one :)
Remove 9th Injector
and in the manual is a 'ByPass bodge' to test the CTS .......which pops and fails for a pastime
TPS at .325 and no huge dead zones
Click to expand...

I suppose you could let the first three items slip a little bit as it was running absolutely fine when Dr Evil had it. The Flapper EFI system is about as basic as you can get and isn't that difficult to fault find if you do it methodically. ;)

As I said, if you haven't got the PDFs, download them, Use the test process PDF and go through each test! When you go through each test write down the results of each one and post them back here. The more we know about each part, the easier it will be to solve the problem. Also when you solve the problem other people will be able to see symptoms and what you did and what solved the problem.

Get testing! :D
 
Last edited:
marccleave said:
Ahh yes, Flapper EFI! I believe the saying is "test don't guess". Now before you go and disturb too much, stop! Also you don't want to start replacing things left right and centre, that can get expensive and you also might end up replacing perfectly good things! :(

Might I point you towards this:

3.5 V8 Flapper system Diagnostic Manual

If you haven't got those two PDFs already, then download them! I've attached them to this post as well, just in case you haven't registered. The two PDFs attached are excellent reading material and cover almost everything!


Now, before you go probing and blaming the EFI system, I've read that youve "played with dizzy timing, checked all connections, checked vac pipes, checked all points on ht leads"

It sounds unlikely that the EFI side would suddenly die through a transplant, possibly timing or air getting in. I don't know as its not in front of me. :) So you've played with the timing, but is the timing actually correct? Do you have a timing light to check? Just make sure the ignition side is okay before you start blaming the EFI. If it idles fine, you rev it and then it dies, are you sure all the pipes are in good condition and not letting any air in? Any unused inlets are covered? etc etc. Make sure everything else is spot on before you blame EFI!

Once you do get down to testing the Flapper EFI, then make sure you go through the list as well:



I suppose you could let the first three items slip a little bit as it was running absolutely fine when Dr Evil had it. The Flapper EFI system is about as basic as you can get and isn't that difficult to fault find if you do it methodically. ;)

As I said, if you haven't got the PDFs, download them, Use the test process PDF and go through each test! When you go through each test write down the results of each one and post them back here. The more we know about each part, the easier it will be to solve the problem. Also when you solve the problem other people will be able to see symptoms and what you did and what solved the problem.

Get testing! :D
Click to expand...

Thanks for the very in depth reply. :)

I say I've played with the timing yes, i have advanced until it was pinking then backed off slightly so seems to idle nicely. But I don't have a timing light unfortunately so don't know if it's actually spot on but i know someone who may have one so will ask.
Also i will check all hoses etc for leaks and double check if there are any unused inlets.

If this fails i shall work through the list quoted to see if my problem lies there.

And will check the efi system as described in the pdf (which i have just downloaded) anyway as i do have a multimeter to hand :)

Again thank you and i will 'get testing' and report back with my findings :)
 
How good is tickover? Smooth ect?
My first thoughts are air leaking into plenum, check pipes are on including ones at the bulk head of the engine.
Could be the ecu as they can be fragile. Where are you.
 
Right then lads bit of an update on this one.

Checked the engine for air leaks with some easy start no leaks found at all and still not revving.
Double checked all electrical connections. Still no revving.

Then proceeded to go through the test procedures in the pdf i downloaded. All was well until i hit test 9. :(

I'm not getting any voltage reading going to the throttle pententiometer at all. Even checked for voltage at the ECU multiplug and getting jack diddly squaut :(


So where do i go from here? I have a pententiometer from a 3.9efi, would that fit and work? if not where else could my problem lie?

Also would you like me to continue with the rest of the test procedure and post all of the results?

Thanks again for the help so far it is very much appreciated :)
 
robbh said:
Then proceeded to go through the test procedures in the pdf i downloaded. All was well until i hit test 9. :(

I'm not getting any voltage reading going to the throttle pententiometer at all. Even checked for voltage at the ECU multiplug and getting jack diddly squaut :(
Click to expand...

(Quick note, you won't get anything if you check for voltages at the ECU multiplug plug when you unplug the multiplug from the ECU as there is a direct connection from ECU -> potentiometer. SO, the ECU has to be plugged in and the readings are taken from the plug at the potentiometer).


Right okay, bit of an explanation here. The throttle potentiometer goes to the ECU pins on pins 2, 3 & 18. Pin 2 is Red, Pin 3 is Yellow, Pin 18 is Green.

The functions of each wire is:
- RED tells the ECU where the throttle is etc.
- YELLOW is a `Vref` ie, Voltage Reference from the ECU.
- GREEN wire is the throttle potentiometers ground.

So from this, and the test manual you should get a constant 4.3 (+/- 0.2) between the YELLOW wire and the GREEN wire. And you say you don't? Thats not good. :( Could you measure this again, but with the pot unplugged? You should still get a constant ~4.3V at those wires with the pot unplugged.

If you don't have a voltage there, then there might be something wrong with your ECU. EDIT: Or a dodgy wire, do a continuity test for each wire, RED YELLOW and GREEN at the ECU multiplug and throttle pot plug. If the pot doesn't get any voltage, it cant tell the ECU where the throttle is and then it won't rev properly etc etc.

As for using a pot from a 3.9 I don't know, never tried, never had flapper and hotwire infront of me to compare.

Try it but I honestly don't know! The throttle pot on the flapper system is 5kohm, measure it and check, then measure the 3.9 pot, if theyre the same and the same pin out, it should work! (Just had a quick google, by the looks of it, it should work as theyre the same but with different plugs on the end. Thanks Land-Rover! :rolleyes:)


robbh said:
Also would you like me to continue with the rest of the test procedure and post all of the results?

Thanks again for the help so far it is very much appreciated :)
Click to expand...

Part of me says yes get on with it, I did and found my ECU was kaput. But the manual says If OK, continue. So its up to you! Try the 3.9 pot and see if it goes...
 
Last edited:
marccleave said:
(Quick note, you won't get anything if you check for voltages at the ECU multiplug plug when you unplug the multiplug from the ECU as there is a direct connection from ECU -> potentiometer. SO, the ECU has to be plugged in and the readings are taken from the plug at the potentiometer).


Right okay, bit of an explanation here. The throttle potentiometer goes to the ECU pins on pins 2, 3 & 18. Pin 2 is Red, Pin 3 is Yellow, Pin 18 is Green.

The functions of each wire is:
- RED tells the ECU where the throttle is etc.
- YELLOW is a `Vref` ie, Voltage Reference from the ECU.
- GREEN wire is the throttle potentiometers ground.

So from this, and the test manual you should get a constant 4.3 (+/- 0.2) between the YELLOW wire and the GREEN wire. And you say you don't? Thats not good. :( Could you measure this again, but with the pot unplugged? You should still get a constant ~4.3V at those wires with the pot unplugged.

If you don't have a voltage there, then there might be something wrong with your ECU. If the pot doesn't get any voltage, it cant tell the ECU where the throttle is and then it won't rev properly etc etc.

As for using a pot from a 3.9 I don't know, never tried, never had flapper and hotwire infront of me to compare.

Try it but I honestly don't know! The throttle pot on the flapper system is 5kohm, measure it and check, then measure the 3.9 pot, if theyre the same and the same pin out, it should work! (Just had a quick google, by the looks of it, it should work as theyre the same but with different plugs on the end. Thanks Land-Rover! :rolleyes:)




Part of me says yes get on with it, I did and found my ECU was kaput. But the manual says If OK, continue. So its up to you! Try the 3.9 pot and see if it goes...
Click to expand...

Right here goes.......

Multi plug was connected for this test as stated in the manual and had no reading.
I did happen to try getting a reading with the throttle pot disconnected also got 0v. (forgot to say this in my last post)

So by the sounds of things my ECU is fubar then?

I have also tried to get a reading using the 3.9's throttle pot and no luck.:(

Will see if anyone local to me has an ECU I could beg/borrow/steal to try out.
And will also carry on with the tests tomorrow afternoon when i get home from work.

Thanks again :)
 
Last edited:
Another update on this ongoing quest to get the buggering thing to rev :p

I now have a reading from the throttle pot test.

4.3V with +ve connected to yellow wire and 0.325V with +ve connected to red wire. Also get a nice steady increase up to 4.4V at max throttle.:D

ECU was taken to a sparky/engineer who is a family friend and the ECU had a dry solder joint which has now been reflowed along with many others.

Happy days!!! :D

Will now go through the test procedure all over again tomorrrow morning and hope nothing else is at fault.:)

Then if all is good hope she starts and actually revs up with no exhaust:eek::D
 
robbh said:
Another update on this ongoing quest to get the buggering thing to rev :p

I now have a reading from the throttle pot test.

4.3V with +ve connected to yellow wire and 0.325V with +ve connected to red wire. Also get a nice steady increase up to 4.4V at max throttle.:D

ECU was taken to a sparky/engineer who is a family friend and the ECU had a dry solder joint which has now been reflowed along with many others.

Happy days!!! :D

Will now go through the test procedure all over again tomorrrow morning and hope nothing else is at fault.:)

Then if all is good hope she starts and actually revs up with no exhaust:eek::D
Click to expand...

Woo hoo! Congratulations so far and good luck with the other tests. My fingers are crossed.

When you do start it and rev it with no exhaust, you have to make a video! :D I've run my 3.5 V8 (strapped to a pallet with two ratchet straps, and it still tried to do a barrel roll! note, i advise against doing this...!!!) with just the manifolds, so no down pipes or y piece and it was rather loud, sounded like a tractor with loud gurgles. When the down pipes and y piece are attached, you get a really good loud v8 gurgle burble as the firing order makes the wonderful sound exiting through one pipe. So when you say no exhaust, what do you have attached? :cool:
 
marccleave said:
Woo hoo! Congratulations so far and good luck with the other tests. My fingers are crossed.

When you do start it and rev it with no exhaust, you have to make a video! :D I've run my 3.5 V8 (strapped to a pallet with two ratchet straps, and it still tried to do a barrel roll! note, i advise against doing this...!!!) with just the manifolds, so no down pipes or y piece and it was rather loud, sounded like a tractor with loud gurgles. When the down pipes and y piece are attached, you get a really good loud v8 gurgle burble as the firing order makes the wonderful sound exiting through one pipe. So when you say no exhaust, what do you have attached? :cool:
Click to expand...

Thank you. My fingers are crossed too along with everything else! :)

And again a big thank you to you and everyone else who contributed for your help it almost had me pulling my hair out/wanting to burn it :eek:

And yes a video will be on it's way once I've fired it up :cool:

Hmmm sounds entertaining firing one up on a pallet...... If i buy another V8 (big possibility) then may try it :D

As for what I currently have fitted....... Literally just the exhaust manifolds :eek: so will take a before and after video when i get the exhaust to fit.
 
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