Dalton1

Anyone have any ideas as to where to look next? I've swapped all the relays I wasn't sure about, as well as inspected and reset ecu connectors and checked as much of the harness as I could for chafing. Took a video of what it's doing but not sure how to get it on here.

Still haven't been able to locate a engine brake relay, there was 5 relays next the the block on the passenger side dash but 4 were labeled "Power Relay" 1-4 and the other was for the power steering fluid low light. I put a new engine speed sensor in, truck seems to start quicker but no change with the engine brake. Is it possible the brake cut out is programed at a higher than normal RPM? It's a former N.Y. dot truck and I know the order some stuff special.

Thanks, I saw those, I figured they were for all the plow lights and controls. on this truck, I'll check them next.

I'm not seeing any relays that appear associated with the engine brake? Any ideas where it might be? Looked in the glove box panel and panel on drivers side firewall.

Yes works perfectly when hooked to an external 12v source bypassing all factory wiring.

Also they are definitely powerleash not Jacobs.

Everything is in adjustment, Brakes work perfectly when direct wired to 12v, even at idle. Still consistently only works over 2k rpms when on factory switch and wiring, cuts out as soon as drops below 2k and comes right back as soon as the engine accelerates over 2k.

The truck has good oil pressure 25-27 at hot idle, only has 54k miles on it. When it cuts in and out its instant like a switch.

Yes, low and high both work, dose the same.

Took another look at the brake, it's definitely electrical as anytime there is power to the head they work, took it for another test drive, engine is only heating up to 175*. Once the engine is over 150* they, work but only over 2000 rpms as soon as you slow down under 2k it will cut out the will come back on over 2k again causing them to pulse off and on. Is it tied into the crank sensor? Could that be causing this? Tachometer seems accurate.

Thanks guys, I will give that a try ASAP I do enjoy it here in Maine, it's been a hot one so far this summer!

It's 728 cubic inch mack engine, 335hp. Basically and E7 with EGR from what I understand, it is painted Grey. There is no check engine lights, I haven't tried to pull any error codes but can check that. Not sure on the model engine brake, definitely a factory installed brake, I assumed it was a Jacob's

I'm looking for information on a problem I'm having with the engine brake in my 07 Mack CV713 with AMI 335 engine. The Jake brake doesn't seem to work under 1800-2000 RPMs then will kick in and be very strong but will kick in and out every 2 seconds, like someone is turning the switch off and on. It does this very consistently. I'm thinking it's got to be an electrical issue, clutch switch is good, not sure how to check the fuel switch on this one. Is it hooked into the crank sensor and could that cause this issue? Any ideas as to where to look would be great appreciated!

Thanks, I did look there but no numbers, I will check the rear behind the head next. Found what looks like where a tag was riveted on behind the injection pump but it is missing.

Thanks! Got a head on the way. Still would like to know if any one has any ideas on how to ID the engine without a data plate??

I'm looking to see if anyone has any info about what heads can interchange with the engine in my truck. Unfortunately the trucks VIN comes back to a glider kit and the engines data plate is missing so I'm not sure what engine I have, its a 2 valve with tip turbine and side mount cooler. Guessing a 285-315? Is there any way to know for sure? Truck is an '82 not sure on the engine, saw a 77 stamped on the side of the head. Engine dropped a valve and I am in need of a replacement head but they are proving difficult to come buy. The part# on the damaged head is 732GB5218B. It does not have engine brakes. Will any E6 2 valve Mack head work or does the part number need to match exactly? Thanks in advance!

Update, swapped the injectors, made no change, cyl 5 still missing, while in there notice the the cyl 5 exhaust valves were adjusted to tight, adjusted the valves and it runs great now, I still get a little smoke but I imagine that's because the engine has close to a million miles on it.

I'll try swapping the injectors tomorrow, thanks! Hopefully that solves it

Update, I checked the eup's by briefly shorting them out, when I short out cyl 5 there is no change, and all the other made it run rougher, so I'm assuming that's the cylinder that's missing. i swapped the #2 and #5 eup's and there was no change, cyl 5 still no change, what else could be causing that cylinder to miss? And how can I test it?

I have a 2001 CH612 with a 310hp E7 Etech that is running rough like it's miss firing and blowing some light grey smoke, no change at low mid and high rpms. The CEL comes and goes, it flashes a 3-4 for engine position sensor, the tachometer is working and seems to be accurate, is it run off the same sensor? Is it the sensor on the front cover? I've ordered a new position sensor but wanted to see if anyone had any thoughts as to what it could be or other things to check. The truck does have very high mileage, 850,000 34,000 hrs thanks in advance!

Name: Mack RD685 (1981) Date Added: 17 November 2014 - 03:07 AM Owner: Dalton1 Short Description: None Provided View Vehicle