Running on two cylinders

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Running on two cylinders

Postby chrisP » Tue 09.07.2019, 13:06

My car has only just stared running on two cylinders, one and three are ok, two and four have given up. I have a strong spark on all cylinders. I don't however have all my tools and manuals to hand. Could someone let me know if we run a lost fuel system, as in, the injectors fire twice per stroke cycle? As I think I have a fuel issue.
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Re: Running on two cylinders

Postby Rambo » Tue 09.07.2019, 13:10

Another one :shock:

Have you seen the recent info. on JohnW's problems with his 2 and 3 cylinder Elan ?

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Re: Running on two cylinders

Postby chrisP » Tue 09.07.2019, 13:48

Oh no, thanks Rambo, I will have a read!!
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Re: Running on two cylinders

Postby John_W » Tue 09.07.2019, 16:14

Yes, the injectors fire in pairs on each stroke, ie according to the Service Notes each injector only delivers only half the fuel needed for combustion each time it fires.

How many miles have your injectors done? My no 1 injector failed electrically at 98,000 miles and prevented no 3 injector from firing also. By disconnecting the electrical feed from no 1 I was able to get 2, 3 & 4 working and drive 2,000 miles home on three cylinders.

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Re: Running on two cylinders

Postby chrisP » Wed 10.07.2019, 12:55

Thanks for the reply John. That is what I thought was the case with the injectors once I had seen that I had a spark. The injectors have about 90K miles on them (they were professionally cleaned about 8 years ago), so it looks like a few people are at the same point. I assume that it is a complete electrical breakdown rather than the injector sticking? I am going to have a play with the car at the weekend and have one spare injector so hopefully that should sort it. Might pick up a full set soon though as well.

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Re: Running on two cylinders

Postby John_W » Wed 10.07.2019, 13:55

Chris,
I haven’t investigated the cause of failure fully. When I replaced all 4 injectors with a new set that I had in the “spares” pile the car was back to normal.

I measured the resistance across the terminals of the old injectors I took out and was surprised to find that all 4 were the same (4.8 ohms from memory EDITED to say the measured values were actually 2 ohms - so much for my memory!). I expected no 1 injector (the one I had to disconnect to get the car running on 3 rather than 2 cylinders) to be much different (either zero or infinite) but that wasn’t the case.

If somebody tells me what voltage is used to fire the injectors I might try connecting a battery to them to check for signs of life in no 1 injector, but there weren’t any while it was fitted to the engine (I tried re-connecting it periodically during my 2,000 mile journey home in the hope that it would magically repair itself and start working again but it didn’t). Any time I reconnected it I was back down to 2 cylinders as no 1 took no 3 down as well.

Good luck with a cheap fix!

John
Last edited by John_W on Mon 15.07.2019, 16:20, edited 2 times in total.
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Re: Running on two cylinders

Postby GeoffSmith » Wed 10.07.2019, 18:14

They're essentially current (rather than voltage) driven devices John. After getting to a peak after a few milliseconds, the current is dropped to the hold level which is typically ~¼ of the peak value. Sticking them on a 12V battery will probably burn them out.

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Re: Running on two cylinders

Postby GeoffSmith » Wed 10.07.2019, 19:01

Thinking about it… the rate of rise of the current is limited by the inductance of the coil and what probably happens on a u/s injector is that the core saturates early if the pintle is stuck. The impedance drops and hogs the current that should go to the paired injector.
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Re: Running on two cylinders

Postby chrisP » Thu 11.07.2019, 13:51

So an injector with a good resistance reading would indicate a coil still intact, it is only the moving part inside that is stuck _ which could be unstuck?
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Re: Running on two cylinders

Postby GeoffSmith » Thu 11.07.2019, 14:19

chrisP wrote:So an injector with a good resistance reading would indicate a coil still intact, it is only the moving part inside that is stuck _ which could be unstuck?

That's my theory - all we need is some practical evidence. :poke:
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Re: Running on two cylinders

Postby John_W » Thu 11.07.2019, 16:15

On another 2-cylinder Elan thread, not far away:
HJ2 wrote:Cleaning won’t help as the problem is electrical. Or else you would have 3 working cilinders, not 2

GeoffSmith wrote:John,
Agree with HJ that it's most likely electrical so probably not worth cleaning.
If it's one injector going down (and dragging the paired one with it) you might be able to get it running on 3 if you disconnect the bad one. Be sure to try disconnecting both as disconnecting the good one may result in there being enough drive to make the bad one operational. If it doesn't improve then it is likely to be wiring or ECU output drive.

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Re: Running on two cylinders

Postby GeoffSmith » Thu 11.07.2019, 17:12

Based on the resistance measurements so kindly supplied by yours truly, I now postulate (all the best theories are likely to change on the basis of new evidence) that it's a mechanical problem causing an change in electrical characteristics. :smt098
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Re: Running on two cylinders

Postby John_W » Thu 11.07.2019, 19:06

I’ll try hitting it with a hammer, then.
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Re: Running on two cylinders

Postby GeoffSmith » Thu 11.07.2019, 20:00

Better than sticking 12V on it.
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Re: Running on two cylinders

Postby alan e » Thu 11.07.2019, 21:21

GeoffSmith wrote:Better than sticking 12V on it.


Or you may want to buy a fuel injector tester it's got 4 pulse modes you can check to see if its opening or not and they only £20 to £25 each.
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Re: Running on two cylinders

Postby GeoffSmith » Thu 11.07.2019, 21:25

alan e wrote:
GeoffSmith wrote:Better than sticking 12V on it.


Or you may want to buy a fuel injector tester it's got 4 pulse modes you can check to see if its opening or not and they only £20 to £25 each.


I should remind you that John and I are scraping an existence on our meagre pensions.
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Re: Running on two cylinders

Postby alan e » Thu 11.07.2019, 21:44

GeoffSmith wrote:
alan e wrote:
GeoffSmith wrote:Better than sticking 12V on it.


Or you may want to buy a fuel injector tester it's got 4 pulse modes you can check to see if its opening or not and they only £20 to £25 each.


I should remind you that John and I are scraping an existence on our meagre pensions.


Is that in your home in England or the one in Spain ?. :D
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Re: Running on two cylinders

Postby Simon_P » Thu 11.07.2019, 23:57

John_W wrote:all 4 were the same (4.8 ohms from memory)
as Geoff mentioned they are current driven peak and hold and Lotus spec is 1.8 to 2.2 ohms. This means that they open fast requiring high current and are then held open with a lower current.

GeoffSmith wrote:Thinking about it… the rate of rise of the current is limited by the inductance of the coil and what probably happens on a u/s injector is that the core saturates early if the pintle is stuck. The impedance drops and hogs the current that should go to the paired injector.
OK I get the theory, perhaps you could give us the proof during your siesta tomorrow.
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Re: Running on two cylinders

Postby chrisP » Fri 12.07.2019, 14:53

Thanks for all the replies, I will find out tomorrow what injector is causing the problems and then put all of them in an ultrasonic bath and see if that makes any difference - will report back......

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Re: Running on two cylinders

Postby Kipperozzy » Fri 12.07.2019, 20:29

Are the testers on eBay for 20 odd pounds any good ?
I also saw relay testers for just over £10 , long lead time from China
Any reviews ?
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