M.O.T emission results , ever seen worse?

ok , so im working from the workshop manual, upto 1994.

Agreed that pin 15 is a permenant live form the battery, however it would have been a really bad design to run an unfused wire from the battery to the e.c.u. The diagram suggests the power comes form tp2(termianl post 2 ) then shows terminal post 2 connected to the battery. The under bonnet fuse box has the 20A fuse in that is blowing. i am putting 2 and 2 together and assuming that this then feeds the e.c.u and relays.

I have tested both relays and they work, they also how power to there poles and 12v to the coils. it appears the E.C.U must sink the current to earth allowing the coild to excite and mak ethe contact. As the E.C.U has no main power then it wont sink this current.

Maybe there is a diagram somewhere in the workshop manual that tells me where TP2 is wired in the engine bay. Might get the chance to look at this on friday so will update on what i find.

There has been a couple of things not in the workshop manual , maybe its just the different variations eg. no cruise control in the manual or maybe i have a 1994 + vehicle , are there any design differences that indicate a 1990-1994 over a 1994 onwards

hmm its the 1994+model as it has lights in the rear bumper according to wikipedia ?

Have you tried a substitute ECU? A long shot but I wonder if there is an internal fault with the ECU causing a short?

Other than that I can only suggest tracing the loom and opening it up (as far as possible) and doing continuity tests. From what you say th eproblem appears to lie with the primary power supplies to the EFI system, so main feeds to the relays would be my first port of call. I would also suggest tracing the loom, find the earth points and give them a thorough clean, remember the injectors are earth switched and there is a power connection from the main power relay to the injectors and the air flow meter - I wonder if that could be an avenue to investigate (just a thought!) Good luck.

the 2 relay for the efi can short to earth by the body of the relay
have had it on mine

Just for laughs my 1991 3.9 RRC was in for MOT this morning. Emissions results:

Fast idle test CO% 0.417, HC 38ppm
Second fast idle tests CO% 1.03 HC 46ppm

Result - FAIL? they used catalyst test limits so will be needing to have a word I think but never mind, didn't change the outcome because I need to replace one of the headlamps.

thats just rubing it in

leclance said:

thats just rubing it in

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Ooops sorry

Mind you, it wasn't a complete waste of time this morning, I was offered their old gas analyser for sensible money so I think I'll be adding that to my collection of workshop tools.

Gas analyser is an awesome bit of tuning gear, i have a very simple Gunson meter that only measures CO but it's ideal for tuning the engine, eliminates the mystery and tells you once and for all what is going on!

Regards the test limits, yeah it is a bit annoying when they do that, mine was tested on the Cat limits aswell, but it would have still failed at 1600ppm HC

Nearly bought one from halfords last week but the wife reminded me that -in her words.

"your not allowed to buy any more f%&^* toys until you get one them working"

Does remove any doubt though so maybe ill try and convince her it came free with a bottle of wine !

leclance said:

Nearly bought one from halfords last week but the wife reminded me that -in her words.

"your not allowed to buy any more f%&^* toys until you get one them working"

Does remove any doubt though so maybe ill try and convince her it came free with a bottle of wine !

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Why not buy her a bottle of wine.

Then buy yourself a gas analyser and hide it in the workshop - I mean women buy shoes and stuff and hide them in cupboards and wardrobes and claim they've been there ages!

classic kev said:

Why not buy her a bottle of wine.

Then buy yourself a gas analyser and hide it in the workshop - I mean women buy shoes and stuff and hide them in cupboards and wardrobes and claim they've been there ages!

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Tactical

Mr Noisy said:

Tactical

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Sometimes! I'm lucky though, my other half understands a bit about motors, when I said I had been offered the gas analyser from the garage and then told her the price she said buy it - Happy days

There is a lad on discovery owners club who has just put up a Gunson gas tester for £50! Used once!

I just paid £85 secondhand on eBay!!

My Rangie has got an MOT! after a bit of fettling this weekend emissions result was

CO% 0.373 and HC 103ppm.

Also picked up gas analyser, it is old but works a treat, measures CO, HC, Lambda, Oil temp and engine RPM. Happy bunny.

Anyway, to the OP, have you got any further?

According to my gunson, my CO fluctuates between 0.6 and 1.2, assumedly due to irregular idle stabilisation.

Either way im happy with that, and that's with the MAF set at 1.00v.

For a laugh we unplugged the MAF, CO was up to 9.5% !!!

classic kev said:

Why not buy her a bottle of wine.

Then buy yourself a gas analyser and hide it in the workshop - I mean women buy shoes and stuff and hide them in cupboards and wardrobes and claim they've been there ages!

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hmm that or they were in the sale ! that old classic

Right im back of holiday so back to sorting this little problem out . Will make a start today when it stops raining and update later. interesting results with the M.a.f unplugged !!

after a morning tracing stuff ! final got to the problem.

The new M.A.F is blowing the 20A fuse.

What a pain in the arse that is ! im sure i had the engine runniing with it plugged in

leclance said:

after a morning tracing stuff ! final got to the problem.

The new M.A.F is blowing the 20A fuse.

What a pain in the arse that is ! im sure i had the engine runniing with it plugged in

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Interesting - not sure the MAF can draw that amount of current, the feed wire is not that heavy. I think you will have to open up the injection loom and trace the wires and look for damaged sheathing and signs of shorting.

One other thought, if yours is running cats and lamda sensors then the system essentially ignores the MAF for fuel trim and uses the lamda sensor output (closed loop). On cat cars, the MAF CO Trim should be set to something like 1.8v. I don't know anything about lamda sensors as mine doesn't have them but I'm sure if you search the forum you'll find some info to help.

O.K. just had a quick look at ECU wiring diagram. If I understand your problem so far, you have a short of some sort causing the main power supply fuse to blow.

The two main relays - ECU power and the fuel pump relay also supply the power for the MAF and the oxygen sensors. The main relay pin 87 gives power supply to MAF and the fuel injectors.

The fuel pump relay off pin 87 is power to oxygen sensors but interestingly looking at this particular diagram (1992) it shows the problem is most likely to be with the fuel pump relay and associated wiring. After the 20amp fuse, there is a 10 amp fuse and this then connects on pin 87 of the fuel pump relay. I am sure these fuses do not feature on the 1991 circuit that I am more familiar with but I think I can better see what you are saying now if that makes sense?

Could I suggest taking out both main efi and fuel pump relays, disconnect MAF and disconnect oxygen sensors then in order plug the components back in one at a time switching the ignition on and off each time and see which component causes the fuse(s) to blow then you can hopefully isolate which part of the loom you need to investigate. HTH