Diesel injection pump question

spider · Post by **spider** » 13 Sep 2010, 20:23

A scope will be sensitive enough to pickup the tiny output from the sensor

, I've not used a scope for about 25 years though ( ! ) and then it was only very basic operations, long since forgotten unfortunately. I could actually do with buying one (long story and not suitable for this topic)

A piezo pickup of somekind will be OK I think, you only need to 'hear' the "movement of" pulses of fuel I would guess, if that makes sense. As you know the vibration will generate a tiny amount of energy in the crystal and you should be able to pick that up on your scope too.

the_weaver · Post by **the_weaver** » 14 Sep 2010, 14:42

I saw somebody posting online saying they'd made up a piezo sensor for an injection pipe by cutting up a piezo sounder from a buzzer. I suppose a sounder might be better, as a proper microphone would pick up noise from the car, as well as the sound of the injection pipe. I had a look at a buzzer I've got and it's the wrong type. It's an old electro-mechanical one with a coil of wire, like a speaker. The best place to get a piezo sounder might be an old digital watch. There's usually a piezo sounder inside the rear lid of the watch to do the alarm sound. It seems that you can cut them to size and they still work.

I thought of another way of checking the timing. If you record the sound of the engine running on a portable mp3 player/recorder, or a computer, and then read the waveform into a wave editor such as Audacity, you can actually see the sounds that the engine is producing, in detail. I'm sure you would be able to see the peaks of sound produced by the cylinders. If you measured the time interval between the peaks you could work out the rpm from that. To measure the timing you would need another sound produced at TDC. I suppose you could put something on the crankshaft pulley to make a noise everytime TDC went around. Something like a circle of plastic with a tab on it, bolted to the front of the pulley, into the threaded holes for the puller. Or you could use the TDC sensor with a circuit to drive a sounder that makes a bleep everytime there's a pulse. It would have to be quite fast though, electronic rather than mechanical.

Paul

spider · Post by **spider** » 14 Sep 2010, 14:46

I'm not sure if you can get away with cutting the piezo up or not, however as you say you can find them in a cheap watch etc if needed. Failing that Maplin Electronics etc (you may have one in your town) ?

Probably better to use an amplifier to increase the (minscule) output from the TDC sensor. Not sure about the sounder, remember with those cheap solid state buzzer things there may be a delay between it receiving a signal and a response, trouble is what is proposed is time critical obviously. Have to remember at idle there's going to be (at a guess say 850rpm) 14 to 15 pulses per second

, not sure how you want to proceed with this, obviously a scope will cope without issue at this (relatively slow for a scope) frequency.

Sorry that's not a lot of help

, I do still think if you set it mid-way you would not be far out, then moving it say 1mm each way to compare

MikeT · Post by **MikeT** » 14 Sep 2010, 15:27

I guess tapping the lift sensor is no good as it's from No3 injector? And looking at those adapters, they all go for the pipe pickup - I assume they sense the shock waves? Adapters are too dear for my wallet. I'm sure it wouldn't cost much to DIY one though, just can't find a schematic to work off.

spider · Post by **spider** » 14 Sep 2010, 15:30

MikeT wrote:I guess tapping the lift sensor is no good as it's from No3 injector? And looking at those adapters, they all go for the pipe pickup - I assume they sense the shock waves? Adapters are too dear for my wallet. I'm sure it wouldn't cost much to DIY one though, just can't find a schematic to work off.

Unlikely to have one at that age, they only fitted them to the electronically controlled (advance) pumps.

Good thought though, I had not considered that at all.

the_weaver · Post by **the_weaver** » 14 Sep 2010, 16:32

Those adaptors are a bit expensive. Too expensive for me probably. I've got my MOT expiring in three weeks so I'm going to be working on the car to get it ready for that. Quite a few jobs to do. Hopefully I can set the timing by ear and get it through the MOT. If I can't get it to run well enough to pass the smoke test, then I might buy an adaptor, if I've got no other option. If I had more time, I would make a circuit to trigger my timing light from the injector pipe. As I haven't got much time, I think the only thing I might manage is to clamp a piezo sounder from a watch on the injection pipe and see if I can pick anything up on my 'scope.

Paul

the_weaver · Post by **the_weaver** » 14 Sep 2010, 16:58

I think there might be another way to check the timing with a 'scope. Put the output of the TDC sensor into channel 1 of the 'scope, and use that to trigger the 'scope. Then connect a normal audio microphone to channel 2 of the 'scope. The sound of the engine will be displayed. I would expect to see the peaks of sound from the cylinders. One of the those cylinder sounds (cylinder number 1) will be just before TDC, the others will be some distance away from TDC. I should be able to display the two waveforms next to each other and measure the time before TDC.

Paul

the_weaver · Post by **the_weaver** » 14 Sep 2010, 22:10

I'm going to try moving the injection pump back to it's original posiition once my half-moon spanners arrive, but I've got a feeling that the pump may be sitting on dirt and corrosion, on it's front mounting area. The triangular shape of the front mounting means that when you turn the pump a lot, it will move from the clean area under the triangle, onto the dirty/corroded area next to the triangle. I might have to remove the pump to clean the corrosion and ensure that the pump sits flat. In the Haynes manual it says to use new washers on the banjo connectors for the fuel supply in/out pipes. I haven't got any new washers. Are these essential or not? Is it easier to pull pipes off instead of undoing the banjo unions, or are they heat shrunk into place? Is it possible to lift the pump out enough to clean the mounting area without disconnecting the banjo unions?

Paul

spider · Post by **spider** » 15 Sep 2010, 11:53

I need to see a picture really.

The banjo bolts you can leave in place (only can visualise a Lucas one though as that's all I have) , they are only the in / out feeds. Just take the jubilee clips of, do NOT disturb the banjo bolts if you can avoid it. But yes you can re-use the washers if you must though.

the_weaver · Post by **the_weaver** » 15 Sep 2010, 23:03

I will take the jubilee clips off if possible. I'm not sure what the clips are. I remember seeing one pipe which looked like it was just pushed over a spigot with serrations. That might be a leak-off return pipe. I never know whether those pipes are just the push-on type, or whether they're heat-shrunk at the factory.

I just checked my timing light (Gunson Supastrobe) and it's got a timing advance feature. So you can set the advance to say 15 degrees on the dial and then just time at the TDC mark on the flywheel. Very handy. Shame it won't work on diesels without that adaptor.

I think you could probably make your own timing light using super-bright LED's. It would be ok for use in a shaded area or in the dark. I've got a Halford's LED torch which is really bright with just three LED's. LED's are probably super-fast in operation and don't mind being switched on and off thousands of times.

Paul

the_weaver · Post by **the_weaver** » 16 Sep 2010, 00:12

Does anybody know when they changed over from M8 to M10 for the access port in the back of the Bosch injection pump? On my 1993 ZX 1.9D am I more likely to have M8 or m10?

Paul

the_weaver · Post by **the_weaver** » 16 Sep 2010, 01:03

I had a look around to see what the prices of those threaded adaptors for connecting a dial gauge to the back of the Bosch injection pump are like. The cheapest I found was 60 pounds. So I thought I'd have another look around to see if there's any standard part that can be bought off the shelf to do the job. The best thing I've found, so far, are threaded hex spacers. RS sell them in small sizes. Here's a link to show what they look like:-

http://uk.rs-online.com/web/search/sear ... &R=1058280

I think there's a company that does much bigger ones. I'm not sure of they sell in small quantities to the public or not, but I expect they might have distributors who do. The biggest size they do, as standard, is M8 by 100 mm long, in steel. The male thread would go into the injection pump. The dial gauge would slide into the M8 threaded hole at the other end of the spacer. Some drilling would be necessary to allow the probe to go through the middle as the threaded hole doesn't go all the way through. A probe could be made from a bicycle spoke which is 2mm in diameter with a 2mm thread on one end which will go into a dial gauge (although a bit loose). A threaded hole would have to be made, in the side, for a grub screw, to hold the dial gauge. Can anybody give me an idea what a typical length of the adaptor would be?

Paul

spider · Post by **spider** » 16 Sep 2010, 15:00

Can't help with specifics regarding 'proper' timing.

I can tell you the Lucas pump has a small blanking plug in the top and there's a blanking plug in the head too (early models), again not really helpful for your case I know, sorry.

Regarding the fuel piping you mention, if is like a serrated effect (clear piping) it is heatshrunk onto the stub, do not remove that as it will not go back without you cursing. Undo the pipe further on if possible (like where it plugs into the filter or something) , you should see some method of removal.

If you are just timing the pump I do not see why you are removing the rubber feed / return pipes ?

the_weaver · Post by **the_weaver** » 16 Sep 2010, 21:43

Andy, I suspected it was heat shrunk as there are serrations visible. I'll leave it alone. I can turn the pump, for timing purposes, without removing the rubber fuel pipes. I was just wondering whether the pump was sitting on rust after the garage turned it. Looking at the pump sprocket it looked like the whole pump might have been leaning a bit.

I've got a 13mm half-moon spanner now and that does the lower mounting nut near the alternator. The upper one at the back I managed to reach with a 1/4" drive socket and a long extension with a universal joint. I never got as far as opening the unions as they were covered in rust and it took me ages to wire brush them.

Once I've disconnected and reconnected the unions I have to bleed the system with the primer bulb. Haynes says "If you suspect air has got to the injectors...." and then goes on about cranking the engine over on the starter with the unions open. I don't have to do this do I? There's no reason for air to get in the injectors if I follow the procedure properly.

Paul

MikeT · Post by **MikeT** » 17 Sep 2010, 10:54

No, you don't have to, they're self-bleeding but if air has got in (you should loosen the unions and pipes if rotating the pump) it will speed up the process if you leave them cracked open when cranking.