Left bank down, no spark, running on 6 cylinder

Well it's not the regulators, disconnected them and swapped them round, no change, bank 7-12 still not running right.

So just to recap,

 

The car was running 100% before, and this is something I keep telling myself, as it hasn't gone anywhere since it was running 100%. So I keep thinking it must be something simple.

 

It was parked up and the following day I started the water pump replacement, once all the bits arrived, I put it back together, but the car didn't run the same. It first only ran on 1-6 cylinders, after discovering the fault was those couple of small broken wires I mentioned, at the coolant sensor and phase sensor, they got repaired and it fired up on all 12. However it has not ran correctly.

 

I also found a broken wire on the TPS sensor, but I also replaced that with a new pin too.

 

To summaries, the car runs lumpy/hunting the revs, odd misfire when running on all 12. If I disconnect bank 7-12, it runs perfect on 1-6, if I try to run on just 7-12, it runs, but poorly.

 

Fuel smell is coming from left exhaust, bank 7-12.

 

The checks/replacements so far.

 

Coils were checked and tested

Ignition modules checked and tested

New HT leads

New spark plugs

New coolant sensors

New thermostat

New water pump

New 02 sensors

New ignition rotor

Distributor cap is the old OEM one, but I tested with a NEW one and no change

Phase sensors volts tested - both read the same

Fuel regulators swapped over - no change

Disconnected fuel lines after the fuel filters - fuel does flow

Swapped the fuel line from left to right banks to see if it makes a difference - no change

LIE computers have been swapped over to check if the fault follows, it never has.

Listened to the Injectors and all sound like they are clicking nicely

Compression test - all show around same results

 

Well I'm pretty much at a brick wall with this issue now.

 

I've gone over just about everything 10 times over, and swapping all know bits from left bank to right, to see if there is any change on the running condition, but nothing changes.

 

The only thing I can think of doing next, is to check the injectors further. I'm thinking of swapping these over too, and see now it runs after that.

 

If there is still no change, then I'm totally stumped. My only options is to ship the car to the UK [im in Ireland] to Mike Pullen, not a cheap option with regards to the shipping cost alone. Here in Ireland we have NO lamborghini dealers or specialists.

 

 

I would try PMing JeffLambo and see what he thinks. Have you tried any injector cleaners?

I would try PMing JeffLambo and see what he thinks. Have you tried any injector cleaners?

 

I put an injector cleaner in today, and ran the car for a short bit, but no change, maybe I didn't run it long enough though.

 

 

Lamborghinisti,

 

 

Hey Sudesh, I've been thinking about your problem and I could only come up with a few things.

 

One, if the computer swap doesn't switch over the problem, it's not the computer. If you are having a miss or rough running with a fuel smell, I would say a plug is off. Since your main body of work was with the distributor, pull the cap and do a connectivity check with a multimeter on each point and to the corresponding lead and measure the resistance. Even twist the lead a bit and see if the resistance jumps.

 

Test with the extenders on and off....again measure resistance. Visually check the extenders for pin holes and arching.

 

My guess is that you don't have all plugs firing.

 

As a laugh...make sure each lead is properly wired to the corresponding cylinder...yeah I know but check it.

 

 

 

While my VT Roadster has coil packs, I have a 91 Ferrari Testarossa as well. It uses distributor caps and extensions like your early Diablo. I've found a fault in the piercing pin hitting the insulation and not the wire lead leading to a misfire.

 

You just have to do a methodical run through on the cap and wires.

 

 

Shamile

Hi Shamile,

 

I keep thinking the same myself. I've not checked the cap with a meter on each point, or the leads in the manner you described. But I did do a spark test etc. Plus I ran a brand new [non oem] cap in there and no change, and I swapped the leads from 1-6 to 7-12 and that didn't help.

 

I've been thinking though, that "maybe" in some way, its the cheap NON OEM HT leads, [even though tests suggest otherwise] but I've ordered a NEW set of OEM Cavis leads from Tim and Evans auto, so waiting now for those to arrive. Tim also mentioned it could be leads and cap too as I sent him a link to the issue I have.

 

So until the new leads arrive, I will run through the checks you mentioned. Plus Ill swap the injectors over too, may as well cancel out another probable cause.

 

Lamborghinisti,

 

 

Hey Sudesh, I've been thinking about your problem and I could only come up with a few things.

 

One, if the computer swap doesn't switch over the problem, it's not the computer. If you are having a miss or rough running with a fuel smell, I would say a plug is off. Since your main body of work was with the distributor, pull the cap and do a connectivity check with a multimeter on each point and to the corresponding lead and measure the resistance. Even twist the lead a bit and see if the resistance jumps.

 

Test with the extenders on and off....again measure resistance. Visually check the extenders for pin holes and arching.

 

My guess is that you don't have all plugs firing.

 

As a laugh...make sure each lead is properly wired to the corresponding cylinder...yeah I know but check it.

 

 

 

While my VT Roadster has coil packs, I have a 91 Ferrari Testarossa as well. It uses distributor caps and extensions like your early Diablo. I've found a fault in the piercing pin hitting the insulation and not the wire lead leading to a misfire.

 

You just have to do a methodical run through on the cap and wires.

 

 

Shamile

 

Well that's the injectors cancelled out.

 

Have to say, removing and swapping the injectors over is a pleasure, 20 min job!

 

I just removed the complete rails with injectors attached, and swapped them over.

 

No change to issue.

Shamile, I read the OHMs as follows,

 

With the HT leads all connected I removed the cap, then put the multimeter + terminal, to the pins at the rear of the cap, the other end of the multimeter terminal, I put at the end of the HT lead [where it connects to spark plug] I made sure to use a good connection there, put a smooth bolt the same size as the spark plug head in.

 

Multimeter set at 2M

 

In order from bank 1 to 12

 

1- .018

2- .017

3- .016

4- .015

5- .013

6- .013

 

7- .010

8- .010

9- .012

10- .013

11- .015

12- .015

 

 

 

 

 

That's close enough not to matter.

That's close enough not to matter.

 

Was thinking that too, was fairly sure it's not the leads, as I swapped them round anyway and there was no change.

 

 

I have to say, you do your troubleshooting pretty quick. I have been meaning to do a compression test on my car for months lol. Even bought the tester months ago and haven't done it yet but finally going to do it today.

If mapsensors is not workning correctly it will run high fuel and the idle will be bad.

 

Check your mapsensors and their connections , there is one for 1-6 and one for 7-12 :

 

 

 

 

If you need some OHM numbers , I give you my numbers.

 

If mapsensors is not workning correctly it will run high fuel and the idle will be bad.

 

Check your mapsensors and their connections , there is one for 1-6 and one for 7-12 :

 

 

 

 

If you need some OHM numbers , I give you my numbers.

 

Hi,

 

Ok, will check that tomorrow, 7.30pm here now and I'm just showered and about to put the feet up for the nite.

 

I'll probably swap the sensors over, and see what the results are, if any.

I have to say, you do your troubleshooting pretty quick. I have been meaning to do a compression test on my car for months lol. Even bought the tester months ago and haven't done it yet but finally going to do it today.

 

lol, yip like to get things done and tested, no point in waiting around lol. Plus I'm a full time dad of a 18 month old boy, so any spare seconds I get between work and taking care of my son, I spend on the car.

 

Compression test is simple, it's just having to do everything 12 times that's off putting lol

Lamborghinisti,

 

 

I was wondering if for the early Diablo if there is a specific way to route the wires...one must cross over here...one there.

 

I used to have a 96 Ford F 150 with wires. In the engine bay there was a sticker that showed that this cylinder wire must cross over this cylinder wire and that cylinder wire must cross over this cylinder wire here.....to prevent cross firing.

 

Anything to show how they "should" be routed?

 

 

Shamile

Good suggestion, but I think I can rule that one out too Shamile, they are not routed in any specific way on 1-6 or 7-12, and 1-6 is fine... also bear in mind that I also swapped 1-6 leads over to 7-12 and no change .

 

 

 

 

Lamborghinisti,

 

 

I was wondering if for the early Diablo if there is a specific way to route the wires...one must cross over here...one there.

 

I used to have a 96 Ford F 150 with wires. In the engine bay there was a sticker that showed that this cylinder wire must cross over this cylinder wire and that cylinder wire must cross over this cylinder wire here.....to prevent cross firing.

 

Anything to show how they "should" be routed?

 

 

Shamile

 

You can also make a temperature test to see if the engine runs the same temperature from 1-12

example: 200 degrees from 1-11 and 12 at 115 degrees, there will be something wrong with no.12 showing 115 degrees.

 

 

I tried doing that yesterday with a meter I have, but found it difficult to get anything accurate as the temp changed depending on "exactly" where the gauge was pointing too.

 

Going to have another try at it shortly though.

 

I did an OHM test on both MAP sensors, pretty much the same on both, .940 on left bank, .990 on the right side, I could swap them round just to be 100% sure.

 

You can also make a temperature test to see if the engine runs the same temperature from 1-12

example: 200 degrees from 1-11 and 12 at 115 degrees, there will be something wrong with no.12 showing 115 degrees.

 

 

 

 

 

On mab sensor: make sure the rubber hose is not leaking.

On mab sensor: make sure the rubber hose is not leaking.

 

I've checked those too, can't find any leaks there.

 

I tried the thermometer I have again, it's not really suited to automotive work, but gives an idea I guess, the header pipes all read fairly close, no real huge dips in temp, although left headers arnt as warm as right side, but not expecting them to be if its not performing correctly.

 

I'll buy a proper thermometer tomorrow

I think that's me completely beat lol, apart from new OEM leads coming, which I doubt will help, I can't really investigate much further or find any faults.

 

I've

 

Fitted new leads [cheaper versions] but still work, swapped those leads from left to right bank to be sure, no change

New spark plug fitted, swapped them from left to right too, no change

New 02 sensors, checked those on the meter and both read around the same

New coolant sensors - also tested by swapping banks over, no change

Map sensors checked and swapped, no change

New rotor installed - even swapped that new one for another new one to be sure, no change

New cap installed - no change

Coils checked and swapped over, no change

Ignition modules checked and swapped, no change

Spark test done, all ok

LIE computers tested by swapping over - no change

Fuel regulators swapped over - no change

Complete Fuel injectors and rails swapped over - no change

Fuel lines after the fuel filters disconnected, fuel seems to flows ok

Swapped those fuel lines over to cancel out it was fuel pressure, no change

Cylinder compression test, no major dips

Vacuum hoses all checked

Phase sensors tested and swapped, no change

Checked the hose from the brake booster to the manifold, no leaks there

Manifold air temp sensors checked and swapped, no change

Wiring checked at all the above and at the connectors, all ok

Got the bulb replaced on the check light, check light now working, but not showing any faults

 

Only other thing I can think off, is still maybe fuel pressure some how? Is it possible it could be fuel pressure even though I swapped the 2 fuels lines around at where they go into the rails?

 

I also find it strange the 02 sensors are reading pretty much the same, cycles quickly from around 140 to 900 on the meter.

 

 

 

 

So Im still having this problem, havent got around to doing anymore investigation until last week and this week, and as the weather is getting better here, i need to get it sorted.

 

Ive been speaking Mike Pullen and keeping him updated on the situation, so yesterday and the previous day we had a few hours conversation on what it could be, yesterday Mike was going through his books/files and advised me to try something I didnt do.

 

So I started the car today, got to running temperature and pulled the 2 fuese [separately] in the engine bay compartment marked power module and electro injectors

 

 

 

Assuming my setup is the same as in the photo above, if I pull fues 31 [1-6 bank] there is absolutely no change in the running sound of the car

 

However if I pull fuse 32 [7-12 bank] the car dies out right away.

 

 

Also, with the car NOT RUNNING but with ignition on [all lights on dash] If I pull fuse 31 and re-install it, there is no sound of any kind.

However if I pull fuse 32 and re-install it, I can hear something powering up and a then a click.

 

So could there be an issue here? anyone kind enough to try the test on their own car?

 

 

Basically just turn your ignition on until the lights display on the dash, [dont start car] and pull and re install the 2 fuses shown in the pic, and let me know if by doing this you get a sound from both?

 

 

Just put the multimeter on to check power on both fuse slots

 

fuse 31 is showing

 

 

 

Fuse 32 is showing

 

 

 

 

I was going to say to swap the fuses and see if there is something different either you have a bad fuse or something in the wiring for the side 31 is on.