Technical 1.6 Cabrio

[renaultvation]

Got home this evening and since the air was moist I thought I would give the car a try. As it wouldn't start I thought I would try some of the suggestions above. First was to run an earth from the engine to the battery, but nothing. Second was gearbox to battery - nothing, so third was mounting bracket holding relays etc to battery - again nothing. Could there still be a dodgy earth somewhere inside the car behind the dash?


Next I turned my attention to the spark. This turned up an interesting result: When I first switched on the ignition, there was a single spark, but when I cranked the engine, there was nothing. I kept repeating it and every time I switched on the ignition I got a single spark.


I know from the noid light that I am not getting a fuel pulse. I am convinced that there is a simple fault which will be easy to fix. Trouble is, I can't find it!

For the record, when the engine is cranking the EML goes out.

 

[blu73]

so seems there is no spark or fuel when its not working, does sound very much like a crank sensor problem, i wonder if one of the wires is damaged or corroded somewhere....

you have a multimeter? I'm trying to remember how a crank sensor is wired, from memory its usually 3 wires, one a permenant earth, which should be easy to test with a meter on continuity, one probe on a good earth anywhere and then other in each pin to check for an earth. The other two will be going back to the ecu so you would need to find the wiring diagram then check for continuity between the plug on the crank sensor and the pin on the ecu plug, should be good solid contiunuity and very little resistance if you check the resistance. If it works but there is high resistance it would suggest corroded wires.

There should also be an earth on the engine loom itself somewhere, maybe a couple - not an engine i have messed with much. I would assume the wiring diagrams are in teh back of the mk1 haynes manual, alas mine is at my mums house and not here so i can't look for you.

 

[renaultvation]

I've checked the crank sensor with the multimeter and it is fine and I also have a spare. I will continue with the earth theory (that sounds a bit grand). Unfortunately the Haynes doesn't include a wiring diagram for the 1.6, but the Porter manual does. I will seek out my magnifying glass!

 

[renaultvation]

Had a brainwave: I ran a connection from the earth in the tester socket to the battery as this shares the same earth as the rest of the ignition circuit. So much for a brainwave, the tide must have been out! Back to the drawing board.

I am pretty confident the problem is as simple as a dodgy connection in the ignition circuit. The problem is finding it. There appear to be more orange wires and connectors than appear in the wiring diagram. I think I have checked every connection under the bonnet. Accessing connections under the dash is far more difficult as everything is so tightly bundled under there.

 

[blu73]

you should have an award for your patience - think i'd have fire bombed it by now... lol

 

[renaultvation]

The fire bombing might nearly be here! The car is not running at all now, which should be an advantage in finding the fault, so I have been methodical in my approach. I have checked the ignition circuits for continuity and all seem well. Similarly, the wires from the crank sensor to the ECU are fine and the sensor is sending a signal. I believe I have a circuit leaking to ground somewhere, possibly on the fuel injection circuit, but I cannot find it. There are dozens of red and green wires connecting all sorts of components, including injectors, EGR solenoid, fuel pump relay and coil. All connections appear sound, but they all seem to be leaking to ground, as does the main feed to the fuel pump. Am I missing something obvious?
Does anyone want an early Cabrio?

 

[Didge3]

Have you removed plugs individually and checked they are all firing when you turn over the engine? (easier done in the dark so you can see the sparks)? Since it isn't running at all now you must'nt either be getting fuel or spark basically.
If it is sparking on all plugs then spray some starting fluid in the intake while cranking, if it coughs a bit then you'll know if its fuel related? Once you narrow down which it is you'll know which to look at first?
Good luck

EDIT: You're also welcome to buy mine I'm thinking of moving it along once I sort out my oil leak, they're basically the same car anyway

 

[renaultvation]

I think I might be winning. I think I have checked virtually the entire wiring loom and all relevant connectors, fuses and relays. I then turned my attention to the control wires to the relays; first the fuel pump and then the ignition. I found no control feed to the fuel pump, so bypassed the relay and heard the pump working. However, when I cranked it there was still nothing. I then looked at the control feed to the ignition relay and discovered only 0.5 of a volt. This pointed to a fault at the ECU. Before giving up, I tried one more trick: I warmed the ECU with a hair dryer for about 5 minutes (the ECU is behind the centre console inside the car) and the car fired up and ran perfectly. I tried it again about an hour later and it started again.
Went out to the car this morning and it was a no start. However, 5 minutes with the hair dryer and it was working again. I suspect a new ECU is required, but in the meantime, I removed the ECU, placed it in the airing cupboard for a couple of hours, then placed it in a plastic bag with two sachets of silica gel and sealed it up once it was back in the car and connected. The test will come in the morning when I see if it will start. In the meantime, I don't suppose anyone has a spare ECU for a 94 1.6. It's a GM unit (below).

 

[blu73]

its a known fault these getting water damage - or at least i have read it many times. Its underneath the heater matrix if my memory serves and a leak there get its wet. Worth some poking around although this is not something i have done before on a mk1 so not sure how easy it is to access and if it means dash out. Sure a search will turn up many threads on it though

Well done for tracking it down and not burning the car lol.

 

[digger58]

Did a heater matrix in my cab last year, not a nice job, Blu you're spot on the ECU is directly under the matrix. Have a feeling I'm going to have to change another one soon in my latest cab as well. Think I will make up a kind of drip tray to prevent future damage.

 

[blu73]

thats a good plan, that or spend a while cutting, soldering and heatshrinking wires so you can relocate it somewhere else perhaps? no idea where but its a thought.

 

[renaultvation]

Today's update: After sitting overnight, Bertie fired up immediately this morning. Looks like my hypothesis might be correct. There is no evidence that my heater matrix has leaked as there is no sign of water on the ECU, it just seems to be affected by dampness in the air. However, if I replace it, I will either keep it protected in a plastic bag, or consider relocating it. I think it should be possible to relocate it on the bulkhead behind the glovebox, as this would not require any modification to the loom.

 

[blu73]

well keep us posted chap, and get some pics of your solution

 

[renaultvation]

I have bought a replacement ECU for £25 from a Punto Sporting. I looked at locating it on the bulkhead, but I could not mount it high enough because of the heater blower assembly. This would leave the ECU vulnerable to damage from feet as it would intrude into the footwell. My solution was to replace the ECU in its original cradle, but in a plastic bag to protect it from any leak from the matrix above. The original ECU is now a spare, kept in its own plastic bag in the boot.
Took the car out for a little blast this evening and it seemed very lively. I suspect this is because the new ECU is from a 1.6 Sporting rather than a 1.6 ELX. The new ECU is a rebuilt unit from ADT which came from a scrapped Cabrio.

 

[renaultvation]

It's been a busy time recently, so Bertie has had little attention, other than a new MOT in March. I had to vacate my workshop, so sold one of my Renault 17s and found a new (much smaller) lock-up for my restoration project 17. This left me with all my spares, which are now all stored in my garage, which was home to Bertie, so he is now sitting on the driveway.
Gave him a good clean today which included giving the roof a good scrub. I cleaned it with tent and gazebo cleaner, then re-proofed it with Renovo. It's come up like new. It was then time for a blast round some country lanes with the roof down.
I have had an issue with the new ECU. It starts fine, but after about 5 or 10 minutes it stutters a bit. If I am on fast road, I barely notice it, but the EML comes on, however, if I am in town the engine dies at low revs. Once it gets past this phase it runs perfectly. I will take it to my local independent Fiat/Alpha specialist to get the codes read. In the meantime, I have refitted the original ECU in its plastic bag with silica gel.

 

[renaultvation]

Plastic bag trick seems to be working well, so I decided to turn my attention to the bodywork. For the last two MOT's I have had an advisory about corrosion near the seatbelt mounts, so today I got underneath to have a look. Indeed there is corrosion on the reinforcing plates mounted to the floor. With wire wheel I set about the nearside removing the remains of the underseal and surface corrosion. I then treated it with rust killer, primed and painted it, then an application of black waxoil.
The offside didn't look so bad, but when I looked closer, although less extensive, it was more serious, with a small hole forming close to the sill and another small area of rot in the floorpan adjacent. I could bodge it, or I can cut out the rot and weld in new metal. I will do the job properly, so need to remove seats and carpet before welding. However, it will have to wait a couple of weeks as I have more pressing jobs on my Jag at the moment which means it has temporarily been reduced to a single seater!

 

[blu73]

However, it will have to wait a couple of weeks as I have more pressing jobs on

Story of my life

 

[renaultvation]

New day and a new problem. Sorted out the welding on the floor at the weekend. Disconnected the battery while welding and reconnected it the following day. While the car was raised I thought I would check the exhaust for leaks, but when I started it seemed to be only running on 3 cylinders. I thought this might be due to damp weather, so left it while I put the interior back. When I started it to move off the ramps it appeared to be only running on one cylinder and unable to move under its own power. I have swapped the coil and the ECU, but it makes no difference. Today has been dry and I have had a heater under the engine with the bonnet open to remove any trace of dampness. I will try again later to see if there is any change.

 

[renaultvation]

Everything is nice and dry now, but the problem persists. I have a spark at the plugs, I have a pulse at the injectors and the fuel pump is working. The engine has suck and squeeze, but little in the way of bang!

 

[renaultvation]

Not sure whether anyone is interested in an update, but you're getting one anyway.
Went to look at new cars today and when we got home I thought I would give Bertie another try. Same as before, turns over, tries to fire, but only manages to limp on one cylinder, then suddenly we are firing on 3 cylinders and pretty soon it is back up to 4. It is now running smoothly and quietly.
Still going to get a replacement as Mrs Renaultvation needs a reliable car. Bertie will be kept though and put in semi-retirement, but can spend winter in the garage.