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Checking injectors for mist pattern?


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When I pull my injectors to check I remove all three retaining plates then withdraw about 3" - 4" and leave pointing at the injector fitting "hole". The petrol spray is then drawn back into the inlet manifold but clearly visible and no, or very little mist escapes the induction vacuum.

 

Only takes a few seconds to run down all six and always seemed safer than jars and upward spraying, or am I wrong?

 

+1 That's what I do but closer, maybe 1/2 to one inch.

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Agree fully with Mike C. Just do not over pull out the injectors as these rely on a spring and that is the simple way these work. No leaks (dribbles) pressure builds up and spring releases its grip and you get a decent spray. For me it has been obvious when injectors are working properly (pulse test try it) after messing about with these things many times; years back I wasted money on replacement injectors that had just a bit of muck stopping the build up of pressure. I am still running a lucas system so on start up I let the pump run for a while to bleed out air; starts and runs like a pig. Volts come up and things go good. Staying with a refurbished Lucas pump although now going to use a direct 12V supply feed through a relay to the pump and get rid of cooling coil around the pump! Let us know how you get on.

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  • 3 weeks later...

When I checked my injectors I didn`t fancy petrol being sprayed for all the above reasons, I made up a test rig using an old disposable gas container for a blowtorch and used compressed air and paraffin (someone will have a comment or two - both about pressure vessels and paraffin)

This seemed to work quite well but i havn`t started the engine yet.

Any comments?

Cheers Neil

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When I checked my injectors I didn`t fancy petrol being sprayed for all the above reasons, I made up a test rig using an old disposable gas container for a blowtorch and used compressed air and paraffin (someone will have a comment or two - both about pressure vessels and paraffin)

This seemed to work quite well but i havn`t started the engine yet.

Any comments?

Cheers Neil

IIRC Lucas' test rig for calibrating MUs used a petrol substitute that reduced fire risk. Dont know what it ,or if its OK for testing injector sprays. Fluid viscosity and surface tension will be important and parafiin might not replicate petrol.

Peter

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I set my PRV with compressed air. At the low flow rates involved, its operation is a matter of fluid delta P vs spring pressure and I'm not prepared to risk petrol spraying around the garage.

 

The shop that worked on my MU and injectors seemed to have used some fluid on their bench that wasn't petrol but they did a good job of recalibration with it -whatever it was.

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According to the Lucas Manual (Little Red Book) the test fluid was

Fawley White Spirit No.100, plus 50 ppm Santolene 'C' Inhibitor or Shell Calibrating Fuel 'C'.

 

That small bible further advises that one cubic centimeter of that the same Inhibitor "should be mixed with 30-50 cc of kerosene" and added to 5 gallons of fuel in the tank, to 'inhibit' the car.

In this age of corrosive petrol, that would be useful advice, if we knew what Santolene 'C' was or where to get it.

Or Fawley White Spirit No.100 for that matter.

 

John

Edited by john.r.davies
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I made up a simple rig from an old cordial bottle with a small air release hole and a piece of silicon tubing (to hold the injector in place) hanging from the underside of the bonnet. Removed all of the sparkplugs and the 12V feed to the coil, then proceeded to check each injector. Worked a treat!

 

post-14246-0-83332900-1512115575_thumb.jpg

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When doing this check into a jar, it takes seconds to spot a good/bad injector, literally one/two squirts. I hang the plug lead of the injector being tested low in engine bay and close to earth so it sparks low down away from the petrol mist. Push the high tension lead over a bolt/extrusion; short it down to 0V. I do not agree with holding spray into inlet in case of a back fire. Also any spare fuel in the bore will spray out so I also place a damp rag over the hole left by the removed injector. Two people, bucket of water and fire extinguisher at hand!

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  • 2 weeks later...

Having just replaced all fuel pipes in the boot and to the metering unit thought I would share the following. I am always careful on not over tightening metal-2-metal joints. However, on the high pressure side these had to be very tight.Modern replacement braided pipe feeding into the PRV was a tight fitting on the threads to the PRV, no not cross-threaded. Joint in engine bay to braided pipe (not metering unit) had to be very tight but then that could be my pipe forming tool. On the low pressure side I have had to tweak the joint to the petrol pump and return from the PRV to tank. Perhaps just me being over careful not to over tighten metal-2-metal joints. Easy check is a little tissue paper (or finger) wiped around the joints.

Hope that helps.

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Having just replaced all fuel pipes in the boot and to the metering unit thought I would share the following. I am always careful on not over tightening metal-2-metal joints. However, on the high pressure side these had to be very tight.Modern replacement braided pipe feeding into the PRV was a tight fitting on the threads to the PRV, no not cross-threaded. Joint in engine bay to braided pipe (not metering unit) had to be very tight but then that could be my pipe forming tool. On the low pressure side I have had to tweak the joint to the petrol pump and return from the PRV to tank. Perhaps just me being over careful not to over tighten metal-2-metal joints. Easy check is a little tissue paper (or finger) wiped around the joints.

Hope that helps.

Or talcum powder which will show up even the slightest weep.

Stuart.

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