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Author Topic: J63 temperature-sensitive engine failure  (Read 131 times)
mhi
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« on: June 28, 2020, 05:34:50 pm »

Last week, in hot weather (by British standards), about 30 C, the Espace had to make its first long journey since March. After about 2 hours of steady motorway driving with the temperature gauge happily in the middle of its scale, without other warning, the engine stopped pulling the car along. Instead of accelerating from 55 mph (90 km/h) to overtake, it slowed down, and down, and down, and I had to stop by the side of the road[1]. As soon as I pressed the clutch, the engine stopped. After a minute's pause, tried re-starting: the engine started well, ran for 30 seconds and died. Waited 2 minutes, tried again: got about 2 minutes out of it this time. We called a breakdown service and waited the usual 50 minutes.

The recovery driver started the engine, winched the car onto the back of his truck, and took us to the next services. The engine was still running, and he couldn't find anything wrong. (I had a slightly entertaining five minutes very politely and gently suggesting that his search for the OBD socket was in vain.) I was given some no-doubt sound advice that it was probably to do with the heat, but might be a temporary blockage in the fuel supply which was unlikely to happen again, the breakdown was officially recorded as "fault not found" and we continued our journey. Later on the same hot day, going the other way along the same road[2] the car did it again: this time we waited 10 minutes, and the engine started happily and got us the rest of the way home.

There was no obvious electrical fault. I looked in the information in the matrasport Vault and the possibilities seem to be (a) fuel not getting to the engine (pump, filter, pressure regulator) or (b) the intake air temperature sensor sending dud values to the engine computer/ECU.

The sensor is 26 years old, easy to get at, and cheap to replace. I've ordered a replacement, thinking that's worth doing anyway. I can't find a data sheet to check whether it has the right resistance.

What are the other most likely causes for this failure? Both times the engine wasn't working very hard in the few minutes before stopping. There were no driver-noticeable symptoms apart from the engine stopping and failing to start immediately, and the hot-for-Britain weather. Is there anything in the Espace or its J7R engine known to fail like this?  I could change the fuel filter but anything more than that means booking the car with my usual mechanic, and I'd like to suggest what to check first if that's necessary.

  - Mark


[1] The A1(M) near Leeds. Thunderingly busy and with a very narrow hard shoulder.
[2] The A1 this time, without a hard shoulder. Less traffic but more scary.
« Last Edit: June 29, 2020, 07:09:43 pm by mhi » Logged

1994 Espace RXE 2.0 (J636)
Anders Dinsen
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« Reply #1 on: June 29, 2020, 06:34:15 am »

Hi Mark

These engines are more or less impossible to break, but fuel supply sounds like an obvious place to look for problems.

I'd replace the fuel filter and the pump. Your problem sounds like one I used to have with my J11, which had exactly the same set up with the same filter type and pump. The brushes on the pump wear down. Additionally they become more noisy. They are sealed at not serviceable. Another source of problems is the fuel pump relay in the engine room. But that would cause a complete stop, whereas your problem sounds like it is just slowing down, not providing enough fuel/pressure etc.

According to my Etai service manual, the intake temperature sensor should have these values:

0 deg C: 254 - 266 Ohm
20 deg C: 283 - 297 Ohm
40 deg C: 315 - 329 Ohm

Good luck!

/Anders
« Last Edit: June 29, 2020, 07:29:59 am by Anders Dinsen » Logged

'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
mhi
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« Reply #2 on: June 29, 2020, 08:06:43 pm »

Thank you, Anders!

The "just slowing down" was at the moment of trying to speed up to overtake, and the engine stopped completely as soon as it was out of gear, not being pushed along by the vehicle's momentum. It's as if something cut out, so it could have been the fuel pump relay or the electronics controlling that.

I have a new fuel filter ready, so I'll replace that as well as the air temperature sensor. My sensor was showing about 3000 ohms at 21 degrees C, and seemed to be an NTC thermistor (increase in temperature decreases resistance), so either it is a completely different part from the one in your manual, or it's faulty. I'll check old and new side by side when the new one arrives in the post.

A new fuel pump is not as expensive as I expected (just checked online) so that seems worth replacing as well. The one in the car still has crimp-on hose clips so is presumably the original, 26 years and 206 000 miles (332 000 km) old. Most of the other electric motors have needed replacing or new brushes by now, so that one doesn't owe me anything.

 - Mark
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1994 Espace RXE 2.0 (J636)
pduke
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« Reply #3 on: June 30, 2020, 03:07:10 pm »

I had a similar -if i understand correctly - problem with my peugeot. It was the idle sensor. It makes sense if you think that the problem was between changing gears or engine not starting from off. In traffic lights i had to rev the engine in order to keep it alive.
Doesn't sound as temperature to me. Also in the glory days of my Espace we travelled all across a flaming europe (i think it was the summer of 15'), 35+ celsius everywhere!, with an already problematic cooling system. It may blew at some point(!!) but it never cut down the engine. Wink
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mhi
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« Reply #4 on: July 01, 2020, 06:11:51 pm »

I have now found Renault technical note NT2173A from 1994, which lists four different computers for vehicle J636 engine J7R 768. The first two have grey injectors, operate at 2.5 bar and use a "CTP" air intake temperature sensor. The second two, one of which must be what I have, use brown injectors, 3.0 bar, "CTN" sensor. I think CTP and CTN are the French equivalents of PTC and NTC, positive and negative temperature coefficient. The Renault part number for the CTN sensor is 77 00 744 583, and that, as FAE 33520, is what I have just fitted.

At 25 C the new and old sensors are about the same resistance (2.81 kΩ old, 2.73 kΩ new) which matches the specification for the CTN sensor listed for other engines in MR299espace1.PDF. For reference, that's

0°C ±1  7469 to 11970 ohms
20°C ±1  3061 to 4045 ohms
40°C ±1  1289 to 1684 ohms.

I have changed the sensor in case it has an intermittent fault, and replaced the fuel filter. Fuel pump will have to wait until next week, since I have only today taken the cover off to look at the old fuel pump to make sure it resembles the one I'm about to pay for (it does). When I turn on the ignition, the old fuel pump makes a normal electric-motor whirr for a second or two and then goes quiet. Not very noisy. Because the fault is intermittent (twice in about 8 hours of driving on the day it happened) that's not surprising. It may be coincidence that it happened in what is (for Britain) hot weather.

Thank you again for the advice and suggestions, Anders and pduke.

 - Mark
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1994 Espace RXE 2.0 (J636)
Anders Dinsen
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« Reply #5 on: July 02, 2020, 07:12:45 am »

That's interesting. I always considered my old ETAI manual quite good, but the Renault techn note is of course better and more exact. I also thought all Espace's were 2.0 bar fuel pressure, and since that pressure comes from the pump, make sure you're getting the right one.

It sounds like the relay and electrical circuit to the pump is all right since its running when you turn on the ignition. The later Espace JE has the pump in the tank so it's less noisy, but it's helpful diagnosing problems like these.

Looking forward to your next "report" Smiley

Best,
Anders



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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
mhi
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« Reply #6 on: July 05, 2020, 11:49:44 pm »

Update: new fuel pump arrived yesterday and fitted today. Cost £29; claims to fit 389 combinations of models and years, including some Alfa Romeo, Citroën, Fiat, Porsche and Volvo models as well as Renault.

It runs, perhaps a bit more quietly than the old pump. So far, just a 60-second test of the engine, to make sure it's receiving fuel and that there are no leaks around the pump. All well for fitting, apart from the usual issues of undoing 26-year-old parts, and that the new pump has a 15 mm spigot for the pipe from the tank, while the original is 12 mm. The rubber pipe stretched enough to go over the new pump fitting, just.

The engine faltered for ten seconds or so before stabilising. That should be the effect of the air bubble which started in the new pump circulating to the engine before being spat back into the top of the fuel tank, and I take it as a good sign.

I took apart the old pump. It isn't as sealed as it looked. I'm not sure what I was expecting, but it was a surprise to find an ordinary brushed DC motor completely immersed in and lubricated by the petrol fuel it was pumping. The brushes are good but the commutator is very worn, not repairable - for cost and safety reasons. Thinking about the way this works, it's running at full speed all the time the engine is operating, irrespective of engine speed or load. Wear will depend more on running hours than on kilometres or miles travelled.

There's no way to know quickly whether this new pump, filter and temperature sensor together have fixed the fault. If it has, I won't be able to be sure for months!

 - Mark
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1994 Espace RXE 2.0 (J636)
Anders Dinsen
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« Reply #7 on: July 06, 2020, 06:25:31 am »

Sounds like you've found your problem, Mark. I'm thinking of the worn commutator. I remember replacing mine and I think taking the old one apart too. Mine often didn't run but could be started by beating it with a wooden rod. I think corrosion killed mine. I was as surprised as you to find the complete motor running in fuel Smiley It makes good sense though when you think about it as it will not only lubricate, but also cool the motor. And that might be where the hot weather might made a difference?

Anyway, it will be interesting to follow. Thanks for updating and congrats on the progress.

Best,
Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
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