Engine ignition troubles

v8alligator · Post by **v8alligator** » Mon Sep 02, 2013 11:40 am

Hi All,

Really hope some one can help with this one.

I have a high compression RV8 Running Flapper EFI system. Powerspark Distributor with Bosch coil, champion plugs and genuine Land Rover leads.

Due to gearbox issues my Land Rover has been laid up for 16 months. I have just put it back on the road and in the time the engine has been resting it has developed a miss fire / hesitation at low engine revs and is not as strong as it once was.

The engine is very hesitant between 750 and 1000 rpm but runs smoothly once the revs pick up. All be it not as strong as it once was.

I have been through the whole EFI system as per the Land Rover test book manual and that seams to be working fine.

The fuel system has been drained as I thought the missing could be stale fuel.

Plugs, Leads, Rotor and Cap changed and has made no difference.

Checked for Vacuum leaks and air leaks around the plenum and AFM.

Still no change.

The timing is set to 7 deg before TDC as per the workshop manual but in reading other posts it is suggested that this needs to be adjusted with the modern fuels. What is puzzling me is why it has developed these problems now as it was perfect before the gearbox went.

Any suggestions or pointers would be greatly appreciated.

DaveEFI · Post by **DaveEFI** » Mon Sep 02, 2013 12:37 pm

Have you checked the fuel pressure?

ChrisJC · Post by **ChrisJC** » Mon Sep 02, 2013 7:53 pm

Does the vacuum and centrifugal advance work properly?

Chris.

v8alligator · Post by **v8alligator** » Mon Sep 02, 2013 9:07 pm

Hi,

I have checked the fuel pressure this evening and both centrifugal / vacuum advance on the distributor this evening and all
Are working fine.

I do think I have found the problem.

When the engine hesitates and misfires I have got oil seeping out of the LH head joint so I think I am looking at a head gasket failure.

The engine has always been dry with no leaks so am confident that this is the problem.

Chris as the engine was your old set up I am hoping you might remember the build spec?

Did you use comp or tin gaskets when you built it? Did you do any valve work? Am hoping it will be a quick strip down and replace the gaskets
Without to much troubles.

I am going to do a compression test to be 100% sure that this is the problem.

Will keep you posted on my findings.

ChrisJC · Post by **ChrisJC** » Tue Sep 03, 2013 5:11 pm

It's composite gaskets with tin-style heads skimmed to compensate for the extra thickness.
I don't recall whether they are stretch bolts or not - you can tell by the lack of washers on the stretch bolts.

Chris.

v8alligator · Post by **v8alligator** » Sat Sep 07, 2013 6:42 am

Hi All,

Yesterday I stripped the engine and took the heads off to see if I can find the reason for the misfire.

The 1st thing I noticed was that the gasket had failed around the front oil way in the RH bank. I am confident that this is the source of the oil flowing out at high revs.

on removal of the spark plugs the RH bank was the normal light brown colour which we would expect from a engine which has run. However all 4 plugs from the LH bank were spotless. Almost like they had been changed and the engine not run at all.
I would expect to see one or 2 which had not been firing but to have all 4 seams strange.
Has anyone seen this before?

Could it be that the gasket had failed and water had steam cleaned the plugs?

For reference the compression test results done prior to removal are.

1 = 184
3 = 164
5 = 158
7 = 185

2 = 178
4 = 182
6 = 185
8 = 180

Regards,

Bryan

ChrisJC · Post by **ChrisJC** » Sun Sep 08, 2013 8:05 pm

Head gasket failure won't let water into the centre two cylinders on each bank, so that definitely won't steam clean the plugs!

A bit mysterious I have to say (although the oil leak doesn't surprise me - the engine in my Landie does exactly the same, so on my Rangie engine I put some silicone around the water and oil ports on the head gasket!).

Chris.

v8alligator · Post by **v8alligator** » Wed Sep 11, 2013 7:12 am

Hi Chris,

Thanks, I did think of doing the same.

Out of interest who machined the heads when you built the engine first time round?

I have just had them checked on the CMM at work to ensure they are still flat and not twisted before I rebuild it on Sunday.

http://s1214.photobucket.com/user/v8all ... s.jpg.html

All measurements are in inches and point 1 - 1 = A and 9 - 3 = U

My only concern is the RH head around the water way is a bit out of spec.

Will let you know how I get on on Sunday after it is all back together.

ChrisJC · Post by **ChrisJC** » Wed Sep 11, 2013 5:32 pm

I can't be exactly sure who did those heads - I have had so many done over the years! They were originally SD1 heads I think, but the main point is that they were 'tin' heads that have been skimmed to make them 'composite'

I think they were done by St. Ives Engine Services, they seated the valves too. This was the first engine I realised the importance of telling the engine builder to get all the valves at the same height so you can get the tappet preload within tolerance on all valves!

Chris.

DaveEFI · Post by **DaveEFI** » Wed Sep 11, 2013 5:40 pm

ChrisJC wrote:I can't be exactly sure who did those heads - I have had so many done over the years! They were originally SD1 heads I think, but the main point is that they were 'tin' heads that have been skimmed to make them 'composite'

I think they were done by St. Ives Engine Services, they seated the valves too. This was the first engine I realised the importance of telling the engine builder to get all the valves at the same height so you can get the tappet preload within tolerance on all valves!

Chris.

Thought the whole idea of them was they compensated for such things? If they don't, you might was well have adjustable ones?

ChrisJC · Post by **ChrisJC** » Wed Sep 11, 2013 7:59 pm

DaveEFI wrote:Thought the whole idea of them was they compensated for such things? If they don't, you might was well have adjustable ones?

They do to a point, but if your valves vary by more than the tappet preload tolerance, you're knackered.

Chris.

v8alligator · Post by **v8alligator** » Mon Sep 16, 2013 11:37 am

Hi All,

I Finished the re-build this weekend and the engine is much more even.

After running it for 15 mins I removed the plugs and carried out a compression test.

1 = 198
3 = 195
5 = 194
7 = 197

2 = 197
4 = 196
6 = 197
8 = 195

There is still a small hesitation on initial throttle opening which needs investigation.

My next plan is to check the fuel pressure to see if this is wrong. Can anyone tell me what pressure I should be seeing? (engine is a EFI Flapper type)

If this is okay I think I am looking at injectors? I am going to try and put a injector cleaner through them to see if this improves things but failing that I am going to be on the hunt for some new ones.

Does anyone know if I can run 3.9 injectors and fuel rail on the EFI system I have? Looking about some people say you can and other say it is not possible. If it does work then I will make the change as parts for the later system are easier to get.

DaveEFI · Post by **DaveEFI** » Mon Sep 16, 2013 12:25 pm

You said you had checked the fuel pressure.

Should be 36 psi minimum vacuum disconnected and something like 28 psi at idle vacuum connected. The last value does depend on actual engine vacuum, though.

I'd also check all the injectors are ok - measure the resistance of each one to make sure one hasn't failed.

Also check the TPS - most are failing these days. Although that generally just makes the engine feel 'flat' when accelerating.

As regards cleaning the injectors etc, it may make a small difference, but I've never had any so dirty they caused miss firing.

Hotwire injectors are high impedance, so you'd need to bypass the resistor pack on the flapper system. But whether the flapper ECU would fire them correctly, I dunno. I suspect not.

Snag with the flapper system is the AFM is a precision electro-mechanical device. Which is old. The ECUs can also suffer from dry joints. Getting both fixed to perfection will cost more than converting to MegaSquirt.

ChrisJC · Post by **ChrisJC** » Mon Sep 16, 2013 5:54 pm

Does that engine have the overrun fuel cut-off connected?, if so, unplug the wires from it and connect them together.

Fuel pressure should be 34-37psi (engine not running - test by turning ignition on and prodding the flap in the flapper to make the pump run)

Could well be an injector problem. Best bet is to get them tested.

Chris.

v8alligator · Post by **v8alligator** » Mon Sep 16, 2013 6:34 pm

Hi Chris,

No fuel overrun installed.

Have checked the injectors out electrically but don't have the means to check spray patten.

I have purchased a uprated fuel pressure regulator from RPI today to see if that improves matters. They have been good and said that if it does not work then I can return it.

Hopefully it will solve the problem.