Sherman M4A2 Detroit Injectors

[Perry Kitson]

If you want the best performance from the engines, don't waste your time on the worn injectors. Exchange the old ones for the GM Reliabuilt factory reconditioned ones. A little pricey, but you wont regret it.

[Malcolm Towrie]

Originally Posted by Perry Kitson

If you want the best performance from the engines, don't waste your time on the worn injectors. Exchange the old ones for the GM Reliabuilt factory reconditioned ones. A little pricey, but you wont regret it.

Perry, we replaced the bad #1 injector with a Reliabuilt injector we (miraculously) found in stock. And then I replaced the bad #3 with one I rebuilt from parts. Both worked well. And the interesting thing is I found nothing obviously wrong with either of the removed ones except I saw a lot of debris when back flushing the injector inlet filters. I pulled the filter on the #3 injector and found lots of flaky debris that was way bigger than it should be, considering we have a fuel filter after the pump. I suspect a collapsed main filter or a total lack of main filter at some point in its life. So I think our main problem is plugged inlet filters. We need to check the filters in the other poorly-performing injectors.
We’re always a bit strapped for cash so just replacing injectors at around $300 a piece for the measly 5 miles a year we put on this tank is a hard option to sell!
Malcolm,

[Malcolm Towrie]

For those that don’t have a tester, I’ve seen a neat way of doing a quick check on an injector. With the injector in your hand, fill the inlet fitting with WD40 using the red straw. Stroke the follower up and down by hand. When it goes solid on you, give the follower a rap with a rubber mallet. You should see a misting spray from all the spray nozzles.
Of the 6 spare tips I have, I found 3 had at least one one nozzle plugged. The N65 tips have 8 nozzles. These nozzles are only about 0.006” diameter so I don’t have anything to poke them clear with. Detroit had a tool that I guess had a 0.005” wire attached to a handle but it must have been very fragile. And anything driven into the nozzle under 2000 psi pressure ain’t going to move very easily.
Malcolm

[Andrew Rowe]

Also another little trick I have observed, is that if you have the return line from the injectors returning to the fuel tank right next to the intake line coming from
fuel tank , you will get air and bubbles sucked into the intake line and then onto the injectors , and it will sound like it is running on 5 cylinders and you think there is an injector problem when there is not. So these two pipes need to be apart in the fuel tank , and also make sure the fuel tank is at least 1/4 full. It is very surprising how much fuel returns to the tank via the 2mm restrictor and then into your normal fuel line, it is like a garden hose full on ! Cheers Andrew.

[Malcolm Towrie]

Originally Posted by Andrew Rowe

Also another little trick I have observed, is that if you have the return line from the injectors returning to the fuel tank right next to the intake line coming from
fuel tank , you will get air and bubbles sucked into the intake line and then onto the injectors , and it will sound like it is running on 5 cylinders and you think there is an injector problem when there is not. So these two pipes need to be apart in the fuel tank , and also make sure the fuel tank is at least 1/4 full. It is very surprising how much fuel returns to the tank via the 2mm restrictor and then into your normal fuel line, it is like a garden hose full on ! Cheers Andrew.

Andrew, yes, I noticed that when test running this engine on the stand. We have a clear return line and saw bubbles occasionally. So we ran with separate supply and return jerry cans.
The tanks fuel tanks are well designed that way. Return comes in at the top of the top tank and has a long path to deaerate before it reaches the pickup at the bottom of the lower tank.
Malcolm