Problems with new Rover 4.6 Engine

[heli_madken]

Thanks SuperV8 I did check that the pointer is at TDC.

Since my last post I have done several things to try and get this engine running well including making a larger bore 'Y' pipe which helped a bit. Then I bought an Ignition 123 Distributor which hasnt really made any difference.

I noticed the other day that one of my welds was a little porous (crap welder) on the manifold so decided to take it off and this is what I found -

Not very clear but look at the exhaust ports, 2 and 8 are how I would expect to see them, 4 and 6 are completely clean like they have never run.

I did think I had a head gasket problem perhaps but their is no evidence of one - not using any water, no steam from exhaust, nothing in the coolant, no scum on oil cap, no clean plugs. I did a sniff test a week or so ago just to make sure which was ok. Not done a leak down test yet.

For the ports to be this clean it would take a hell of a leak on those two cylinders but I cant believe I have been driving on 6 cylinders all this time is there anything else that could cause this?

All plugs are identical, a little on the white side which shows some overheating but all the same.

Assuming there isnt another reason for this the obvious culprit would be the injectors, all are new 4 hole Bosch units. What should I be seeing with a test meter from an electrical point of view?

Anyone come across anything like this before, any thoughts and help would be appreciated.

[scudderfish]

If you suspect the injectors, swap 2&8 with 4&6 and see what happens.

[SuperV8]

I have had poor wiring connection with some of my injectors in the past - from my old original wiring loom.
I traced it back to weak spring contacts in the a couple of injector connectors. I small tweak with a screw driver and hey presto singing on all 8 again.

As you have separate exhaust headers its is easy to tell if any cylinder aren't firing by their temp difference.

[heli_madken]

Thank you for your help.

Compression test done, this is on a cold engine throttle closed only trying to spot any obvious problems -

Figures are as if you are looking at the engine -

8 - 122
6 - 100
4 - 110
2 - 117

7 - 117
5 - 116
3 - 119
1 - 119

So the two suspect cylinders are lower than the others which is not good but I would have thought with 100/110 PSI cold and no throttle I would still get enough compression to fire the cylinder?

Will do a leakdown on those two cylinders next.

Could the low compression be a break-in issue if these cylinders have not been firing properly?

[heli_madken]

Noid light shows that electrically 4 and 6 injectors are getting a firing pulse

[SuperV8]

I would suspect the low pressure on those two cylinders is as a consequence of those two cylinders not firing and the rings not bedding well?

Check the resistance of the injectors - at the ECU plug, which will also check the connector to injector contact.

[stevieturbo]

Noid light shows that electrically 4 and 6 injectors are getting a firing pulse

So if you are sure they are getting a valid signal, then swap those injectors with another cylinder. Or if wiring reaches, swap wiring from a good cylinder, to the bad cylinders and see if it moves.

Also confirm you have spark on those cylinders.

And that the valves/rockers do open/close as expected.

Get a heat gun when running to determine if those two pipes are colder than the rest.

[heli_madken]

I think its a running in issue as well so I have skipped the leak down test for now just working on getting the injectors out.

I get 4.2 ohm for both the left and right hand banks so all looks well there

If I cant see any visible issues with the injectors then I will do as you say stevieturbo thanks for the help

[heli_madken]

I have the injectors out, nothing that I can see blocking them in any way

They all have the same internal resistance of 14.8 ohm and applying 12v gives a nice audible click.

I think I am going to put them all in my ultrasonic cleaner, take off rubber seals first

Anyone think of an effective way to test spray pattern?

[heli_madken]

Change of plan, I have ordered a small tester off Amazon so I wont do any cleaning until I have tried this, hopefully it will confirm that the two suspect ones are blocked or partially blocked

[SuperV8]

I have the injectors out, nothing that I can see blocking them in any way

They all have the same internal resistance of 14.8 ohm and applying 12v gives a nice audible click.

I think I am going to put them all in my ultrasonic cleaner, take off rubber seals first

Anyone think of an effective way to test spray pattern?

Check the resistance of each injector at the ECU connector end.
You need to ensure each injector connector is fully connecting.
Easiest to do this at the ECU connector.
From the wiring diagram you can find the pin out number of each injector wiring pair - just use you multi meter to check this resistance on all injectors.

[heli_madken]

Thanks for your help, I checked between pins 2 and 13, 2 an 11 and got 4.2ohm for both which is within spec for all injectors connecting.

I think I am pretty happy that electronically all the injectors are ok. I am hoping that testing tomorrow shows a physical blockage, if not I am back to square one.

[Ian Anderson]

Are you getting cross firing? So the HT wires cross over coming out the distributor.

When in the dark…start the engine and see if there is arcing between some wires.

Ian

[heli_madken]

Thanks for you help Ian, I have checked that in the past but its something else I can look for when I get the engine back together.

Tester arrived but not very conclusive on results. What I hoped to find was two clogged injectors but what seemed to happen was after a few spurts of the carb cleaner they started to spray just the same as the others. Whether the cleaner dislodged whatever was there I dont know.

There is a flaw I think with the cheap tester I bought in that you are relying only on the pressure from the spray can cleaner so all you get to see is a stream of fuel coming out of the 4 orifices which is certainly not atomised in any way. Personally I dont think this shows how they truly behave under 38 PSI of fuel feed.

So I thought I would send them out to get them checked but then thought I would simply buy two new ones as they are only circa £30 each.

Going to run them all through the cleaner anyway. Bit dissapointed I was hoping to have a definitive answer today

[stevieturbo]

The injectors have clips that secure into the rail, you can lift the entire rail out and crank with injectors all pointing into jars.

Although whether that's easier than just swapping to different cylinders and re-trying...debatable. But sometimes a visual can help.