Another 3.9 RRC tale of frustration.

**PhilipA** · 13th September 2011, 07:40 PM

During my recent trip to Cape York the engine started to get a loud knock at about one tappet speed. This occurred about 5KK after I fitted a new cam, chain and tappets from Autopost UK.

I changed the oil at Cooktown, and the noise diminished completely. the old oil had done about 5K and was changed after a 1000Km run in. I was surprised how black and ****ty it looked, so it must have still had lots of assembly lube even after a 1000Km initial change.

However at about Maryborough I noticed that power appeared to be down at higher revs and there was a definite regular miss sound in the exhaust at bigger throttle openings and higher revs.

I arrived home on Saturday so decided to try and find the cause.

First thing was to change the fuel filter, but it looked OK with not much sediment. I then ran a diagnostic using my 14CUX fault reader. No faults.

Next took the compressions, and on taking out the plugs It was evident that number 6 was the culprit as the plug was oiled up. I replaced the plug with a known good one but no joy.Plugs are Iridiums about 15KK old and all a lovely colour except 6

Compressions came out at 145-150Lbs except for 6 which is 170Lbs.( I thought due to carbon, but maybe now think a valve not opening)

I then placed a "Colortune "in 6 and could see that there was combustion at under 2000RPM but above that it faded to nothing after about 2 seconds. Checked the resistance of the wire (Magnacore) at 11Kohms and then took the lead off to see an excellent spark up to about 13MM or so.

Ah Ha I thought, looks like a dud injector , so I changed all the injectors for a set of Bosch gen111s that I have. I had Bosch gen11s in the motor.

Anyway, the effort was wasted as it is just the same, although it has picked up a lot at idle and will not idle under 1100 RPM. I suspect that one or more of the Gen111s are leaking air as they do not have a retaining slot , and can easily be too high or low.I fitted some zip ties to ensure they didn't drop under fuel pressure but I may have overdone it! ( I cannot easily reach them as the Thor manifold gets in the way!)

Funny thing is that the base idle speed was OK with the stepper disconnected and I found the stepper jammed fully open( although I may have trashed it as they open fully on shutdown. It will not now extend) I fitted another that I had and it closes but the idle will not come under 1100.

Oh I also tried another 14CUX ECU that I have. No difference.

I am now thinking that it is cam, lifter, pushrod or rocker related,which really annoys me as it is a major job.My bet is a crap quality cam that has worn down or a collapsed lifter.There is some tappet noise now but not a lot, so it must have clearanced itself! Grrrr.

YES the cam was run in properly. At least I know where to look.

All ideas and suggestions appreciated.

I may try another fuel pump, as in addition to the consistent loss of one (or more) cylinders it also seems to miss more under hard acceleration.

BTW, the ignition is via a Mitsubishi amplifier(sold by Bosch) via a Bosch 717 coil controlled by a Unichip with electronic advance curve so it is not the dreaded Lucas meltdown.
Funny thing it that it cruises smoothly at 2000Rpm or so on light throttle but doean't like hills. At least the bottom end seems good.
Regards Philip A

**milld** · 13th September 2011, 08:12 PM

Could it be a partial broken valve spring? Surely the cam & lifters can't wear that bad in that short of time.

**PhilipA** · 13th September 2011, 08:27 PM

I guess all will be revealed when I take it apart.
I would think a broken valve spring would cause the valve to sit partially open and I would have low compression.
Crap lifters could break the internal spring and just have the pushrod wobble up and down .
Regards Philip A

**LRCounty** · 13th September 2011, 09:09 PM

Hi Philip,

When I had similar symptoms, it was a rocker failing where it contacts the valve stem. The pad must have come loose, then fallen off, then the aluminium slowly disintegrated. Eventually it ran on 7. At some point it went from tapping to being reasonably quiet, which may have been when the pad came off totally.

The fact that an oil change eliminated the noise may point to something different, but rockers are easy to have a look at....on my motor anyhow

Regarding Gen III injectors. I had the same problem. Under pressure they were forced down and caused leakage at the top. I found a post from a guy who sells them, suggesting an o-ring in the next groove above the lowest o-ring. It lets the lowest o-ring slide into the manifold and seal, and prevents the top o-ring from popping out of the fuel rail...problem solved.

Regards
Andre

**disco 3 door** · 13th September 2011, 09:58 PM

Hi Philip, just a long shot, have you tried the Throttle position sensor. A mate had similiar problem with lack of top end power especially under load. Regards Shane.

**PhilipA** · 14th September 2011, 08:02 AM

Thanks Shane ,I looked at it yesterday but ran out of time to do a test.
At the moment I am concentrating on the 7cylinder problem .

Certainly my MAF is OK as I disconnected it to check whether the diagnostic tool was working and got a 12 error.(as the diagnostic tool stays blank if no errors). A bad TPS should also show as an error . There are three possible errors

17 Throttle Potentiometer
18 Throttle Potentiometer high while Airflow Meter low

19 Throttle Potentiometer low while Airflow Meter high

Regarding Gen III injectors. I had the same problem. Under pressure they were forced down and caused leakage at the top. I found a post from a guy who sells them, suggesting an o-ring in the next groove above the lowest o-ring. It lets the lowest o-ring slide into the manifold and seal, and prevents the top o-ring from popping out of the fuel rail...problem solved.

Thats a good idea Andre. Thanks, although it may be easier to refit my Gen11s. I will do some measurements and see how it goes.
I almost went nuts over the stepper!
Regards Philip A

**chazza** · 14th September 2011, 11:20 AM

The running symptoms sound the same as mine

After replacing the camshaft and followers and NOT running them in properly it has worn away one lobe

**Grumbles** · 14th September 2011, 12:30 PM

What does "running in a camshaft" mean or involve please?

**400HPONGAS** · 14th September 2011, 01:33 PM

PhillipA , what were the comps again ,both Wet and Dry
"Compressions came out at 145-150Lbs except for 6 which is 170Lbs.( I thought due to carbon, but maybe now think a valve not opening"
If a valve dont open ,then you dont get any air into compress,thus it should be Lower .Perhaps that cylinder has excessive "Oiling" due to incorrect fitment/gap alignment/bedding /glazing up of the rings . (although someof these issues should result in Lower Comp .
Was the Plug oiled up or wet from unburnt fuel .When the combustion ceased at over 2000rpm was it still sparking or did it lack fuel and/or air ?
As for "running in a camshaft" thats only the end process
Correct preparation ,pre-lubing,knowing what you valve spring loadings are (although RV8 are so light it wont matter ) .
correct preparation
Soak and bleed all lifters , spray bases of lifters with Moly spray before inserting.
Spray cam with a good quality Moly running-in spray , Atv least 2 coats drying off between each coat (the crap grease that comes cams is usually worse than not using it !) When fitting cam coat liberally with oil before inserting .
Pre-lube engine through oil pressure port for a serpy or Hand drill on the shaft for a early type , prepack gears with Vaseline before starting on a early .Prime oil filter.
make sure all the rocker shafts and rocker to pushrod , rocker to valve all get a a good coat of the Moly spray before atempting start up.
All the grease type pre-lube stuff can get wiped off before it actually fires it up .
Excessive cranking over without good oil pressure can ruin all your good work , avoid it !!
Use a running in oil like Penrites running in oil .
Now that all the Prep is done , and your sure you have a good chance of getting good oil pressure , then kick it in and run it up to 2000 rpm , for 10 mins .Watch the temps and pressures . After about one HOUR of running (around da joint), drop the running in oil ,and change to your favourite drop .
The magic stuff to build engines with
Wet Film Assembly Spray HE50

Wet Film Assembly Spray HE50 | Blackwoods

**PhilipA** · 14th September 2011, 02:04 PM

Yes beeutey I did all of that.
The cam was parkerised but I also lubed each lobe with Moly assembly lube .
Ran up the oil pressure with a drill. It had oil pressure from start up. It didn't crank but started straight away.
Ran it at 2000RPM for 20 minutes.
Warm comps yesterday were
1= 145 3=150 5=145 7=150
2=150 4=155 6=170 8=150
So really all good. ( funny even with different heads the LH bank has read 5PSI less than the right. Deck height difference?)There was a lot of carbon in 6 using a borescope. The plug was fuel wet but still firing,it just didn't get hot. The mixture is OK blue with a touch of yellow at low revs.

The plugs were all OK when checked at Moreton Telegraph station ( to try an ascertain where the noise was)and the engine has 207KK on it so ring glazing should not be an issue.

All lifters were soaked for 24 hours and depressed in oil. Rockers to pushrod and pushrod to lifter were moly lubed and valve stems also. I suspect the lifters as 2 became easy to push down when depressed in oil, and I replaced these.

Regards Philip A

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