Man, it's just one thing after another with this car sometimes!

You may have seen a few of my other threads recently. I started out replacing a belt tensioner arm and pulley, and decided to do the vacuum pump as a "since I'm already there" kind of thing. Before the job, the car was running well enough, other than the odd noises that were starting to come from tensioner pulley and arm bearings, which were completely shot.

Anyway, everything was going fine until I was installing the new VP and I over-torqued one of the bolts and snapped the head right off. I put everything back together as best I could, hoping 5 good bolts of 6 would do the trick. The car continued to run fine, but had developed an oil leak (from the VP, of course), so I parked the car in the garage for a few more days.

I finally got the snapped bolt out without too much trouble. Reinstalled the new-ish VP with brand new hardware. Was extra careful to tighten all 6 bolts gingerly in a cross-wise manner, first by hand and finishing with a half-turn or so with a ratchet. Hooked up the brake booster line.

Before I moved on, I wanted to make sure this thing wouldn't leak, so I went ahead and started it without putting the serpentine belt or fan back on. Started right up, I mean, quicker than maybe it ever has in the year I've owned it, but in a couple seconds it started idling really rough and knocking/pinging/nailing or whatever you want to call it. I shut her down (which seemed to take longer than normal) and took a closer look - realized I hadn't hooked up the other line coming off of the vacuum pump. Okay, so that would explain the delayed shut-off, but would it have anything to do with the idle?

I hooked the other vacuum line up and tried again. Nope, same story. I took another look and realized the vacuum line I had hooked up wasn't properly seated on the barb, and was possibly leaking. But again, would a vacuum leak even affect idle on these engines?

Where I'm at now is waiting until tomorrow to put the fan and serpentine belt back on, going for a drive, and seeing what happens. Maybe it just has to do with sitting for a couple of weeks? I don't know - but I don't see what I could've done to noticeably affect idle quality through a simple VP R&R - especally sine I just dod the very same job without negative effect (other than the snapped bolt).

Any ideas?

__________________

I would suspect an air leak on the fuel system, nothing to do with the vacuum pump.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

The vacuum pump and system has NOTHING to do with idle quality. As suggested above, check for an air leak in the fuel system. If the car sat for a while, it could just need to be driven.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

it probably just needs to be driven.. didn't you also just put in new injectors or nozzles not too long ago?

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

IIRC engine shutoff sources vacuum from the brake booster line, not the smaller VP fitting. Are you sure you didn't touch other vacuum lines that might be directing vacuum to the shutoff actuator? Is the ELR connector at the back of the IP is properly plugged? Are the tach and AC working?

Sixto
83 300SD can be yours
98 E320s sedan and wagon

I've been suspicious of this for a while. The car takes a while to start sometimes, not a crazy long time, but more than I think it should. Starts quicker with a little throttle, glow plugs & relay check out, no smoke or low power - it just reminds me a little of the way the car cranks longer after changing fuel filters, and it's still bleeding air out (although obviously not as severe). I'm inclined to try replacing all the fuel lines under the hood, and either bypass or replace the fuel thermostat. I also have a fuel tank screen in hand, just need to get around to draining the tank sometime (which seems like a major PITA).



Yeah, injectors rebuilt with Monark nozzles about 2 months ago. Hopefully it does just need to be warmed up. Something else I thought of is that I was listening to the engine while in my garage and with the hood raised - so maybe it always cold idles like this, and I just never noticed? Anyway, gonna give it a drive and see how it does with a little throttle and warming up - I was worried because something just didn't sound right.



I did undo some of the vacuum lines that route through the firewall between the main engine compartment and where the airbox is, so that I could remove the fan shroud more easily. But that's all EGR stuff, and as far as I know would only result in boost being cut if disconnected - and the engine wasn't on boost at all. also, I'm pretty sure the vacuum lines were hooked back up, even if the solenoids (or whatever they are) weren't bolted back to the firewall.


No idea about the ELR connector - is that the electronic idle control? I haven't touched the IP at all (other than removing hard lines for the injectore R&R a couple of months ago), but I also have never inspected/adjusted this vehicle's idle controls. I thought there was supposed to be a numbered dial or something to adjust idle RPM, but I haven't found one.


Didn't notice the tach or blower fan (I didn't want to run the engine very long or drive anyway, on account of the still missing serpentine belt). Are you thinking maybe OVP somehow? I changed the relay not too long ago, sometime over the winter.

__________________

I think if you have extended cranking, you have an air leak which will cause rough idle. Also, if you are draining the tank.. Don't bother touching any hard lines. Don't waste your time and invest in a mityvac fluid extractor and do it through the back. Take out the fuel tank sender (its a 46mm socket 3/4), but instead put a large pair of vice grips on there or channel locks and take it off. It has very little torque and evacuate the gas once your below a quarter of a tank and on reserve.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

For 124s only the '87 300D/TD has an ELR trim dial. All I meant is ensure the 2-pin ELR connector on the aft end of the IP is properly plugged. Also when cranking and idling make sure the stop lever is fully in the run/unstop position. I've seen vacuum problems manifest as the stop lever not going fully up when the key is turned to glow and bobbing while cranking and idling. Quick check is disconnect the engine stop vacuum line then start the car. First make sure the stop lever stops the engine and/or have a 14mm wrench handy to loosen injector lines.

Sixto
83 300SD can be yours
98 E320s sedan and wagon