Monthly Archives: December 2016

Sensors and an unfortunate incident of unplanned ingestion

I’d planned for a while to change the intake air temperature sensor on the Renault because it had been reading a little “odd”- erratic and not really reflective of the world in general.
I ordered a replacement part- the closest I could get in terms of fitment is for a 1991 Jeep. The thermistor curve is the same as mine, as is the physical fitting. The only difference is the wiring connection.

undo

I don’t have a 19mm crow’s foot so slight tool abuse saw the old sensor undone.

old sensor

The offending article. Rather grubby (not that it really affects it) from being in the flow of fuel and air.

closeup

Closer inspection shows that the thermistor bead is cracked. That’ll be why the readings have been a bit strange.

comparison

Comparing old versus new. Same, barring the socket.

tools

Head inside into the warm to get set up with the tools required- I don’t have the proper Jeep socket so I decided that the heat of the engine in the location shouldn’t be so high to melt solder, so I would reuse the original connector.

chop chop

A quick spin of the Dremel later and the connectors are exposed.

trimmed and soldered

Trimmed the lugs down and soldered the old wires on.

heatshrink

I’d added a couple pieces of heat-shrink tubing to the wires before soldering them on. Fired up the propane torch outside to warm them up to shrink them down to the wires.

heatshrunk

A little bit toasted but shrunk down nicely.

reinserted

Inserted the new sensor and connected it all up. Noticeable difference now on cold start, before the oxygen sensor warms up and begins to give trim readings.

computer monitoring

I took the car for a drive and it was a lot better. When I got back I popped the hood to check on things and in doing so, leaned on the airbox, which was stone cold- that’s wrong for this kind of weather as the preheat damper valve should open up and draw warm air in from around the intake manifold. Took a bit of a looksee at what was going on. The vacuum operated valve was working when vacuum was applied to it. I took the throttle body hat off and found this:

thermo-valve

That’s about one-third of a thermostatic vacuum valve that controls the intake preheat damper flap. The rest of it is… gone. That will likely be the bad misfire the other day and the reason for the plugs being covered in dirt and having closed up, with bits of the valve being drawn into the cylinders and bashing about at the insides.

boroscope

I borrowed the 1979 Edmund Scientific fiber boroscope from work to have a look inside to see if there was anything left in the manifold that needed to be removed or any damage to the inside of the engine.

intake poke

Pushed it down the intake and had a look inside the manifold.

air sensor

It’s a bit difficult to get pictures from but that’s the new intake air sensor down the intake towards no.1 cylinder.

Took the plugs out and had a look in the bores.

crown

Top of one of the piston crowns. They all looked good. Put the mirror back on and took a look at the valves.

exhaust valve

Exhaust valve- looking good. A few signs of chips in the deposits in pots 1 and 2 but nothing substantial, thankfully. Looks like it broke up and was ejected in pieces out of the exhaust.

5 volts

Took a few readings from the throttle position sensor as it was acting a bit weird. Measured OK, and came up better after having been reconnected, so probable cause is a bad connection at the device. Back up and running, but I need to go to Dodge to see if they have the thermostatic valve.

Finding a leak that doesn’t exist, and a broken timepiece.

I’ve been having a hard time finding a few problematic issues with the Renault lately. Particularly it had started to leak power steering fluid quite badly, which would mark the floor where parked up and also get onto the auxiliary belt and make that slip.
Looking down from above, past the alternator and air conditioning compressor the pump looked rather wet, so I splashed out $14 and bought a full seal set for the pump. I decided to clean everything up with degreaser and refill the system, to hopefully see where the oil was leaking from.

dismantle

Begin by taking everything out, including battery, battery tray, moving the air conditioner comressor, remove the alternator and the brackets holding it all in.

empty

That leaves good access to the power steering pump. The corrugated plastic tube is the wiring for the front of the car, the braided hose is the gravity feed to the pump from the reservoir.

scrubbed up

Cleaned up the pump with an old toothbrush and engine degreaser. Rinsed it all down with warm water from the potato pump.

clean

Got a bit carried away as I had water left, so I cleaned down the inside of the hood where the oil had flicked off the belt, and the surrounding areas also. Topped up the oil and left it to dry overnight an in the sunshine.

full

Left it for two days, then checked on the level. Unfortunately the oil was all there still.

still oil

Another two days. Nope, there’s still all the oil left in there. The leak has miraculously fixed itself. Normally, hot, cold.. didn’t matter. It would leak regardless of it it was run or not. Now it’s not leaking!

clean pump

The pump is clean and dry, no signs of leakage.

oily frame

The only other place I can see is the return line, from the rack back up to the reservoir. If that has a crack or a pinhole it could be leaking. The engine cradle frame is a bit oily down under the back but I cannot see anything else that would be causing a leak. Further investigation to follow.

The second thing that irked me was the previously well-working clock had quit.

broken display

The display had taken to showing mostly nonsense, or nothing at all.

clock out

Took the dash to bits (again) and liberated the clock from the little cubbyhole it’s attached to.

polished

Cleaned up the smoked plastic section of the clock as it was all scratched and hazy.

components

Figured there were a couple pieces that might have failed and caused it to not work. Replaced the electrolytic capacitor and transistor. No joy.

circuit diagram

Followed the traces and built a diagram of what went where, to get a bit of an idea of how it all worked.

dead

Tested it but the chip was dead. No oscillator, just noise. The clock circuit boards are available, but they are a Jeep Wagoneer part, and as such suffer heavily from Jeep Tax and are therefore expensive.

zeroes

Upside-down image but poking power to the grid brought some nonsense up on the display so the VFD was all still good.

9

Poking about a bit more showed that some of the logic was alive, as various numbers could be liberated. Nothing sensible though.

led

Purchased a little LED clock with voltage and temperature capability for ten bucks, with the intention of fitting it into the clock as shown- looks OK but a little out of place and the very-bright display has no dimming capability.

dismantle

Decided to strip the board down and re-use the VFD, with the new clock module providing the logic. I’ve ordered a little 50V boost converter to drive the VFD, that will be proven to work first then I shall go ahead and get some high voltage transistors, pull the LED’s off the clock and use the output (multiplexed in the same way thankfully) to drive the VFD. Original clock, original display, just now with time, temperature and voltage display. Watch this space for updates.