rhinoo

Thanks for the reply. I didn’t check that the way you said but yesterday I disconnected that line at the intake and applied a little bit of shop air with a rubber tip blow nozzle and held it there for a few seconds and when I pulled it off the tube it was still holding air pressure. I may try what you said tomorrow though. Did put a new lift pump on today and still have same exact pressures as I had before. Back to the drawing board.

Thanks, I was thinking the same thing and didn’t see why running it under a load would raise the pressure at all but it was an expensive pump and easy to reinstall to try it. I will try to run straight from a bucket of fuel tomorrow to see what we get.

Thanks guys. Took it for a road test and still low pressure. When making boost pressure would drop to 11psi and when let out of the throttle it would bounce between 20-25psi

This wouldn’t reflect lift pump pressure though right? I don’t mind to look into that but the lift pump pressure is half of what it should be apparently. Thanks

Ok, it has new filters and tanks were clean. I will pinch return off to see if it changes. I did remove the pump and the cam in the injection pump looks good.

Pressure is checking low. I guess I should try a lift pump? The pics are of idle and wot.

Ok, thanks. Is the mechanical a good thing or bad? Trying to get teed into fuel system now but gotta go pick up a fitting. I talked to a guy at Rochester diesel earlier and he said that if someone put that s400 on without upgrading the injectors that it would be sick. I told him I was gonna check fuel pressure first and if it was ok I would call him back and order a set of injectors.

I’m looking at truck now and has no ecm, manual foot throttle, with Bosch inline pump.. I sat on phone with Kentuckiana Mack for 30 mins for them to tell me it was an e7-350. 🤦‍♂️

Also wanting to check fuel pressure today. Do you know what it should be coming out of lift pump? Thanks

Ok, is this engine a vmac l or vmac ll? Or something different?

Ok, I will check to be sure check engine light is working when I key up in the morning. I did already change the air intake boot on turbo because it didn’t look real good when I serviced it. I was looking all of them over closely earlier tonight and there is another one that doesn’t look great either but haven’t checked for leaks. Is there enough pressure when idling that soapy water would show a leak? Vin# 037403… if that turbo happens to be upgraded I guess I would need to check injectors to see if they are upgraded also. Should this truck at least puff a little black smoke? Especially with lugging and turbo not spoiling up?

Yea, I think that is the next step if the turbo is correct. Can I tap in at the inlet on secondary fuel filter?

I did do a full service on it once I got it home. No check engine light.

Got a new to me 98’ 688s with an e7 350. I noticed a slight turbo lag when I test drove it but once I finally hauled a load the lag was worse. It seems to take a few seconds to get under the turbo before it picks up. No smoke at all. I actually choked the motor out twice down shifting going up a hill. The shift was made in plenty of time but the turbo delayed so long the motor kept going down. The second time I tried to drop 2 gears but it still didn’t pick up in time. If I keep the motor wound up it does decent. I own several trucks and drove them all, even a Mack 96’ 613 with an e7 427 and it doesn’t fall on its face like that at all. So, I was thinking maybe not getting enough fuel but I was also wanting to make sure it has the correct turbo on it. Does anyone know what turbo should be on this motor? I was thinking tomorrow I will also try to check the fuel pressure. Does anyone know what it should be?