It will reveal bad injectors, you want all the results to be 35ml or less and you want them all to be fairly even.

It's a quick cheap test to do yourself but it does not prove an injector is good. Injectors may have valve issues
and a poor spray pattern which a leakoff test will not show.

Some will say it's not worth it but if your doing it yourself then I think it's worth doing, cheaper than paying
a garage to bench test each injector.

 

Thanks. i am not looking for a solution to any problem that I think I have; just interested.

If an injector appears to be within the acceptable range, it could still have a poor spray pattern and therefore not be up to scratch?

Seems that a leak-off will tell one only that an injector may be OK but is certainly in a bad state. It can't tell one if the injector is AOK?

 

Its more to quickly and fairly cheaply tell you which injectors are bad without paying for a benchtest
which maybe needed if everything else checks out fine and it passes the leakoff test.

Often though the leakoff is enough to let you know all is not well.

 

Thanks. Think I knew that in the distant reaches of my brain.

But if the injectors are either giving too much fuel or too little, surely there must be some different engine noises or smoke? With too little, is the engine 'struggling?'

 

My daughter's TDi Renault Modus was smoking badly with the exhaust smelling of diesel and the mot looming. I did a leakoff test, and the leakoff results were 30, 30, 30 and 35. All within spec, you could argue, but it was the 35 one that was causing it. Changed that injector and it sailed thro' the mot.
My Mondy, a few years ago, failed the smoke test, did a leakoff test and one injector, that funnily enough had given a knock threshold fault 2 years earlier, (but which cleared when I recoded it) was a tad higher than the others... bought a nos replacement and bingo! mot passed OK.
I don't think that a garage is capable to do anything other than a leakoff test, for a bench test you'd need to take them to a fuel injection services place as they have the equipment and ability/knowledge to conduct comprehensive testing, c/w a printout of results. I had mine done 3 years ago, cost £12 each + vat.
Low frp can be caused by a faulty injector(s) leeching too much pressure from the pump, a leakoff test can reveal which is the culprit.
In short, it's a very cheap and useful addition to any diagnostics and I would recommend a leakoff test as a 1st step before starting to shell out wads of cash on parts.

 

Going away for a 'much needed break' ( how I HATE that phrase!!) and will do a leak-off when we return. Don't think there is any issue and the FRP seems to be fine, but interested to see the results.