Lumpy 3.5 with Flapper

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richardpope50
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Lumpy 3.5 with Flapper

Post by richardpope50 »

A friend of mine is trying to get his RV8 3.5 or maybe 3.9 with a flapper EFI (in a Dax Rush he built) working and he is not an expert on engines. In fact he finished the car two years ago and when it did not work he lost interest so left it. It's either a 3.5 or maybe a 3.9 and the engine was built by RPI or similar with new dizzy and most bits and bobs.

So a friend and I have offered (next week) to see if we can get it running so he can get the car on the road.....

I understand that it does start and does run but very lumpy as though a cylinder or two are down on each bank. Whilst we will check timing, spark and all the usual things but it could be injectors.

1.) Can I check these injectors with an LED test bulb to see if they are at least triggered? Any other way to check them?
2.) Does anyone have a simple suggested check list of what else could be wrong? As engin professionally built, I doubt it is compression and such things.
3.) There seems to be a proper RV8 Flapper diagnostic manual floating around. Does anyone have a copy I can download?

Any pointers for next week would be helpful.

Thanks.


Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by ChrisJC »

The Range Rover Manual is here:
http://www.cowdery.org.uk/downloads/FlapperManual.zip

I would check the injectors with an oscilloscope. Whatever you do, don't put 12V on them as that will destroy them.

Chris.
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Re: Lumpy 3.5 with Flapper

Post by DaveEFI »

There are two injector drivers in the ECU, one each feeding each bank of injectors. Each injector has a series resistor to limit the current through it. They are in a pack mounted beside the AFM, and you could check each individual one with a DVM. Should be about 6 ohms. And clean the connector. Injectors should be be about 2.5 ohms.

Several ways to check each injector is getting a pulse with the engine running. Perhaps the easiest is a noid light - you can buy them on Ebay. Or a LED with something like a 1k series resistor. A 'scope would be best, but not many have one. If you have an automotive DVM, the Dwell function (originally to check dizzy points) will give a reading too.

But none of those really checks an injector is opening and passing the correct amount of fuel - although the display on a scope may show a stuck one.

The big snag with a system which was installed on a different car and has never worked is there could be a number of faults.

Don't rule out the ignition system either for the same reasons. If the new dizzy is a Chinese copy, they have rather a poor reputation. IMHO, misfiring on a flapper is far more likely to be an ignition problem.

The Land Rover guide linked to is very good, but it is a very time consuming process to check everything properly.

One other thing to check is that there is a 6800 ohm resistor fitted between the coil negative and the ECU feed from that.

If you send me your email address, I'll send you my re-drawn flapper schematic showing the true wiring colours, etc, which makes it a bit easier to follow, and as a PDF, so can be zoomed in etc without going fuzzy.
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Re: Lumpy 3.5 with Flapper

Post by SuperV8 »

With my 3.5 flapper I was getting rough running, like it was running on 5 or 6 cylinders. With separate headers its easy to check which cylinders are down by touching the headers - the ones which don't burn you are't working :shock:

Mine was down to two problems,

Injector issue - a couple where not working, found my using a small battery (I think 3v - NOT 12v) across the terminals, should be able to hear/feel a click. Got hold of another set of flapper injectors and rigged up a simple test bench to get 8 good ones.

Connector issue - found by unplugging the ECU connector and going through each one with a DVM as in that fault finding doc linked previously to ensure the expected value. Couple of connectors weren't connecting so I tweaked the contacts with a small screwdriver and hey presto.

Tom.
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Re: Lumpy 3.5 with Flapper

Post by DaveEFI »

Can be worth removing the injector rail complete with injectors, and place over blotting paper. Crank, and look at the pattern from each injector. Any big difference should be apparent. But observe safety precautions when doing this. :D

IIRC, you can make the injectors fire by pumping the throttle with the engine stopped, but ignition on. A stethoscope should let you hear each one clicking.
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Re: Lumpy 3.5 with Flapper

Post by richardpope50 »

Thanks guys for your help …

1. Many thanks for the manual.

2. I do not have an oscilloscope.

3. Whatever you do, don't put 12V on them as that will destroy them.

OK, I won’t.

4. There are two injector drivers in the ECU, one each feeding each bank of injectors. Each injector has a series resistor to limit the current through it. They are in a pack mounted beside the AFM, and you could check each individual one with a DVM. Should be about 6 ohms. And clean the connector. Injectors should be be about 2.5 ohms.

I’ll do this test.


5. Several ways to check each injector is getting a pulse with the engine running. Perhaps the easiest is a noid light - you can buy them on Ebay. Or a LED with something like a 1k series resistor. A 'scope would be best, but not many have one. If you have an automotive DVM, the Dwell function (originally to check dizzy points) will give a reading too.

Dave, you made up such and LED tester for me when I had problems with my own engine so will use that as you suggest. I also have a Dwell meter.


6. But none of those really checks an injector is opening and passing the correct amount of fuel - although the display on a scope may show a stuck one.

Agreed.

7. The big snag with a system which was installed on a different car and has never worked is there could be a number of faults.

Agreed.

8. Don't rule out the ignition system either for the same reasons. If the new dizzy is a Chinese copy, they have rather a poor reputation.

Agreed. We have genuine spares so will check this out.

9. IMHO, misfiring on a flapper is far more likely to be an ignition problem.

Good in that it may be easier to find.

10. The Land Rover guide linked to is very good, but it is a very time consuming process to check everything properly.

Thanks for warning.

11. One other thing to check is that there is a 6800 ohm resistor fitted between the coil negative and the ECU feed from that.

You mean an inline 6,800 resistor in the wire from the coil to the ECU.

12. If you send me your email address, I'll send you my re-drawn flapper schematic showing the true wiring colours, etc, which makes it a bit easier to follow, and as a PDF, so can be zoomed in etc without going fuzzy.

Dave, you have it but sending it again. Thanks.


13. With my 3.5 flapper I was getting rough running, like it was running on 5 or 6 cylinders. With separate headers its easy to check which cylinders are down by touching the headers - the ones which don't burn you are't working

Perhaps an obvious check!

14. Mine was down to two problems,

Injector issue - a couple where not working, found my using a small battery (I think 3v - NOT 12v) across the terminals, should be able to hear/feel a click. Got hold of another set of flapper injectors and rigged up a simple test bench to get 8 good ones.

Connector issue - found by unplugging the ECU connector and going through each one with a DVM as in that fault finding doc linked previously to ensure the expected value. Couple of connectors weren't connecting so I tweaked the contacts with a small screwdriver and hey presto.

Useful tips / checks. Thanks.

15. Can be worth removing the injector rail complete with injectors, and place over blotting paper. Crank, and look at the pattern from each injector. Any big difference should be apparent. But observe safety precautions when doing this.

IIRC, you can make the injectors fire by pumping the throttle with the engine stopped, but ignition on. A stethoscope should let you hear each one clicking.

Sounds a last resort but thanks.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by ChrisJC »

DaveEFI wrote:
Wed Sep 26, 2018 8:51 am
One other thing to check is that there is a 6800 ohm resistor fitted between the coil negative and the ECU feed from that.
You don't need to worry about that - I never bothered with it.

Chris.
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Re: Lumpy 3.5 with Flapper

Post by DaveEFI »

ChrisJC wrote:
Wed Sep 26, 2018 5:49 pm
DaveEFI wrote:
Wed Sep 26, 2018 8:51 am
One other thing to check is that there is a 6800 ohm resistor fitted between the coil negative and the ECU feed from that.
You don't need to worry about that - I never bothered with it.

Chris.
Interesting. The purpose would be to reduce the current flow through the input stage on the ECU. I'd guess added as they had found a possible problem with that.
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Re: Lumpy 3.5 with Flapper

Post by ChrisJC »

If you open the ECU and have a look, you will find it goes through another 10K with a capacitor to GND. So all I can think is that it is for EMC reasons, perhaps making the radio sound better!

It definitely doesn't protect the ECU in any meaningful way.

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Re: Lumpy 3.5 with Flapper

Post by richardpope50 »

Thanks and I'll leave the 6,00 resistor to the very last point if the others do not sort the issues out.

Making a start on Monday .... Will let you know the reult(s).
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by DaveEFI »

richardpope50 wrote:
Fri Sep 28, 2018 5:49 pm
Thanks and I'll leave the 6,00 resistor to the very last point if the others do not sort the issues out.

Making a start on Monday .... Will let you know the reult(s).
Other thing is many flapper looms are in poor condition - the insulation cracks and can fall off where it has got hot. But usually at the ends close to a connector to an injector or sensor. But it's quite easy to dismantle a connector and fit sleeving. Also, it's common to find injector connectors which have broken on removal. You can fit the later Junior Power Timer ones - as used on the hotwire - which are more robust.
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Re: Lumpy 3.5 with Flapper

Post by richardpope50 »

Thanks Dave, another check on the list.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by richardpope50 »

Had a good day testing and found ..
1. Injector connections for 4 & 6 swapped around.
2.Vacuum advance pipe attached to wrong inlet on distributor’s adv / retard control.
3. Timing slightly out.
4. Injector 4 ..... below

Currently the engine ticks over very sweet and sounds as though it is running on all 8. However, blip the throttle and run at 2,000 to 3,000 rpm and it sounds as though there is a definite miss-fire although otherwise all is fine - it was backfiring at high revs until we adjusted the timing. This is all in driveway as we cannot drive it on the road – not licenced and needs work to do this.

Initially we could not find any trigger signal for injector 4 when testing with an LED tester on the JT connection. In fact, we could not get a signal for some time. Then all was OK so just possibly there is a faulty connection.

We think it is more likely to be ECU / EFI problem so plan to go through Rover’s EFI diagnostic manual tomorrow to check everything out. However, there is a nagging doubt that it is ignition as the miss-fire just seems to sound like an ignition problem and not like a shortage of fuel. HT leads all new and good spark. Coil is fine as swapping it made no difference. Plugs new too and so is distributor cap and rotor arm.

Anyone any suggestions apart from going through EFI manual checks?
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by richardpope50 »

Does it matter which way up the AFM is installed? I noticed that the installed unit is 90 degrees to the standard Land Rover installation.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Re: Lumpy 3.5 with Flapper

Post by DaveEFI »

Each bank of injectors (1,3,5,7 2,4,6,8) are wired in parallel, with those connections inside the ECU. Very unlikely a problem inside the ECU is one isn't working. Unplug the ECU and measure the resistance between the individual injector pin and the +12v feed on the main relay ( marked 87 on the relay, wire colour brown/yellow) The loop resistance should be 7-10 ohms for each circuit.

Swapped connectors on the injectors on the same bank doesn't matter, as they are all in parallel.

On the SD1 Forum and on here, there are reports of new poor quality dizzy parts around, often branded Lucas. Rotor arms a favourite.
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