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Checking injectors for mist pattern?


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I want to check my injectors for spray pattern;

I believe I have the push in type. I was told to remove one injector at a time, place tip in to a jar and check the mist pattern.

How do I remove them

Once removed, do I start the engine and let it run or have someone crank it without starting it?

Do I remove the plug wire to the cylinder being tested?

What should the mist pattern look like?

 

Thank you all again

 

Sam

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Have the engine warmed up and running.

Beforehand, loosen and remove the retaining plates that secure the injectors. They won't fall out - they are being sucked in!

 

Have a large jamjar or catering coffee tin to hand.

Pull out the first injector - grasp its butt, NOT the line! - and hold it into the jar/tin.

The spray should be an even pyramid, a bit narrower than an actual pyramid, with no absent segments, stopping and starting briskly with no dribbles.

 

Don't look at it for long - there are six to check, and the jar can fill up! But beware of allowing the injector to spray across the engine. Hot surfaces and electrics don't mix with a petrol spray. Or rather they do, but you don't want them to.

 

As you remove an injector, the engine will accelerate, as the vacuum drops to atmospheric and the M/u goes to max fuelling.

 

John

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After having a small fire start from no. 5 injector, for no apparent reason, using the above method I now remove the spark plugs to reduce load on the starter then run the injectors into 6 separate jars. With someone operating the starter I then lift each injector only enough to observe the spray pattern.

 

When I do this I also tag no 1 spark plug lead and leave the plugs in the HT leads resting on earthed metal but well away from the injectors.

 

To make this easier I'd welcome any suggestions as to a convenient place to connect a remote starter button to energize the starter solenoid from the engine bay, if there is one.

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And how many people actually survived this procedure?

 

Is it possible to, 1st, warmup the engine; 2nd, shut engine, then remove injectoe and place in the jar; 3rd, restart the engine and check for pattern?

 

Should I remove spark plug wire to the cylender I'm checking?

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I don't see why the engine should be warm . I check the injectors with a cold engine but make sure the fuel enrichment lever (choke) is off . I remove the spark plugs to reduce load on the starter and make the engine spin faster ( it spins a lot faster)- giving good indicative spray patterns .

 

I don't like any accidental engine fires, once they start they must be quickly extinguished before they get out of hand- hence the members' comments above on keeping fire extinguishers nearby.

 

If you are worried about the spark plugs as an ignition source pull the LT lead on the ballast resistor when you remove them.

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Don't worry about it too much Sam. Fwiw, I pull the injector out and direct the spray onto thick cardboard then put the injector back in. I can then look at the spray pattern as it's drying on the cardboard. If the injector needs bleeding the invert as Neil says and tap the side of it. That usually encourages the air out of it.

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Neil surpasses himself!

Advice not only obscure, but if interpreted literally, dangerous!

A faceful of petrol wouldn't be nice, if sprayed over the engine - see above.

John

John

You have obviously been shown the wrong way to do it. Glass in hand good luck with that.

Edited by ntc
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To make this easier I'd welcome any suggestions as to a convenient place to connect a remote starter button to energize the starter solenoid from the engine bay, if there is one.

Just use one of these http://www.ebay.co.uk/itm/Sealey-Remote-Starter-Switch/191756450578?epid=1823120009&hash=item2ca5933b12:g:Cy0AAOSwcB5ZJVwh

Stuart.

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Or one of these - it has a black rubber cover over a button that closes the solenoid contacts on hand/finger pressure.

It will replace the original solenoid - ifthat doesn't have such a button.

https://www.canleyclassics.com/price-list/?search=121269

 

John

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I understand Mikes concerns.

This job has serious safety aspects, but yet there appears to be different opinions / approaches between the experienced contributors, also in older posts.

Please bear in mind the fact that a method that is safe when followed by experienced hands may not be so safe if less experienced people (like myself) attempt to follow, even if skilled mechanics.

Can we try to get to a common "best practice" on safety critical jobs?

Petrol has an auto ignition temperature of approx 246-280 degr.C (it has a range).

At this temperature, NO spark is needed.

With lower temperatures, a fuel-air mixture and a spark of sufficient size are sufficient.

 

To reduce risk on this job we could:

 

1) Avoid sparks:

Remove the 12V feed to the coil.

In this manner we cannot do a test with a running engine but the absence of sparks reduces risk; off course, voltage is affected, which affects pump operation (pressure). Question is if this affects the purpose of the test, which is testing the injectors.

 

2) Temperature-Cold engine:

If we do the test with a cold engine, we are below the auto-ignition temperature of hot parts of the engine (the exhaust manifold in particular).

 

3) Errors, failures:

We should always anticipate on (small) human errors or failures, like unintended dropping of an injector, a breaking glass jar, fuel in the eyes, a rupture in the nylon fuel line etc.

 

4) Have a Plan B

Have a fire extinguiser at hand and a 2nd person present.

Also have the car outside, should things go really wrong.

The 2nd person can also turn the ignition key, but even better is a 3rd person whose single task is to watch the safety aspects, this common practice nowadays in many industries but may seem overkill here.

If you were involved in a serious incident, this changes your mind-set.

 

I would be intersested in feedback/comments from experienced testers, you can't beat combined experience.

 

Regards,

Waldi

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Someone must surely have had one light up....and lived to tell the tale.

 

The volume of fuel per squirt at tickover is not great, a few cubic millimeters. So I'm fairly sanguine about the risk even if the spray form a single injector ignites. Wear leather glove and be ready to stuff the burning injector back into its hole and not panic.

 

Peter

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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?

 

 

Alan

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Someone must surely have had one light up....and lived to tell the tale.

 

The volume of fuel per squirt at tickover is not great, a few cubic millimeters. So I'm fairly sanguine about the risk even if the spray form a single injector ignites. Wear leather glove and be ready to stuff the burning injector back into its hole and not panic.

 

Peter

Mine caught fire when I pulled No. 5 injector while testing the injectors with the engine running as described above. There were no problems with testing nos. 1 to 4. As I've had engine fires in other vehicles in the past I knew that time was of the essence so I quickly replaced the injector into its hole and blew the fire out without really thinking . The fire was small when I extinguished it with only slight melting of the nylon injector line where it connects to the injector, fortunately the rest of the line was not heated up long enough for it to blow out..What bothered me was I could see no obvious source of ignition- although Waldi's comment above on auto ignition would answer this. I have tubular steel extractors just below the inlet manifold which would warm up fairly quickly.

 

Personally I'm not prepared to repeat the hot test procedure.

 

Thanks Stuart and John for the comments on starter operation. I have a remote starter button as shown on Stuart's link, I'd just like to know if there is a convenient place to connect it without having to get under the vehicle - my engine bay is pretty busy above the starter .

Edited by Mike C
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If you want to see all the injectors firing together, then you need a well-charged battery, or else jump leads from another car with a running engine, so as to remove hot surfaces and active sparks well away.

And, you need a rack to mount the injectors in. Just dumping them all in a coffee tin produces a maelstrom of jets, difficult to see if any are faulty or not.

 

I made up a rack from folded alloy sheet, pop-rivetted together and sealed with Red Hermatite.. It holds the injectors separately, lets you see the jets and catches the spray, although as shown, I sit it in the coffee can to catch the overflow.

 

So, two methods! Neither is risk free!

John

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post-535-0-75604800-1509876741_thumb.jpg

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Or one of these - it has a black rubber cover over a button that closes the solenoid contacts on hand/finger pressure.

It will replace the original solenoid - ifthat doesn't have such a button.

https://www.canleyclassics.com/price-list/?search=121269

 

John

Not on a 6 it wont as thats on the starter.

Stuart.

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You are right, of course, Stuart, I suffered from the confusion that conflates the 'starter solenoid' that sits on a 'pre-engaged" starter, to throw the pinion into mesh with the starter ring, with the separate 'solenoid switch' that starters with a Bendix drive use.

 

In the first case, it should be easy to rig up a thin wire from the starter solenoid terminal to the battery. Touch that to the battery to make the engine whizz!

 

Me, I prefer to turn the engine by hand to do valve gaps etc. See the "Show & Tell" thread to see my 'special tool'!

John

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Feel the injector pipes as described in the operations manual as you should feel a good "hard" pulse on each injector pipe. Be careful that you are not feeling another pipe pulsing. No pulse then spray into a jar and check for dribbles; gently tease out out the end of the injector ( whilst running) to clear out any dirt stopping the base from sealing. I generally have some one start for me as it takes seconds to spot an issue. Start engine and you should immediately have a good "cone" spray and then stop engine avoiding having too much petrol spray. Just be carefull as it is only a spring holding back the nozzle until pressure causes a release of fuel. Fire extinguisher and bucket of water good to have at hand. Another method I have found is to go very fast and clear "muck" out that is stopping the injector base sealing and stopping the build up of pressure so that it sprays properly. Fast method is my favourite!

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Feel the injector pipes as described in the operations manual as you should feel a good "hard" pulse on each injector pipe. Be careful that you are not feeling another pipe pulsing. No pulse then spray into a jar and check for dribbles; gently tease out out the end of the injector ( whilst running) to clear out any dirt stopping the base from sealing. I generally have some one start for me as it takes seconds to spot an issue. Start engine and you should immediately have a good "cone" spray and then stop engine avoiding having too much petrol spray. Just be carefull as it is only a spring holding back the nozzle until pressure causes a release of fuel. Fire extinguisher and bucket of water good to have at hand. Another method I have found is to go very fast and clear "muck" out that is stopping the injector base sealing and stopping the build up of pressure so that it sprays properly. Fast method is my favourite!

I suspect that a plug of air seems to sometimes "bounce" in the injector line and stop the fuel flow. For totally dry lines, like after installing the MU I find that this can be generally cleared by pulling the tips of any offending injectors until fuel flows.This can be done with the engine cranking quickly (plugs removed).

 

For engines that are running a few minutes operation above 3000 or so rpm seems to blow the air out and establish good fuel flow.

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