Hard Start, White Smoke...

[rustyk]

Recently, my AMG has become cranky to start after sitting a few days since the last run. Once started, it runs normally. A few weeks ago, the cranking was slow, but a new battery and starter cured that.

Anyway, my first thought was the injector fuel return lines, but they're new (with the 2-yr old Peninsular Diesel engine) - they checked out fine. Return line to the tank appears to be intact.

I'm now suspecting the lift pump - possibly either it but more likely the "start" circuit that activates the pump.

So far, I've assessed the problem to be one that fuel in the supply line (about 15' in my diesel pusher) is draining back to the tank and aerating the injector pump on cold start, and the lift pump may not be powering up with the key in "start". If I attempt a start a couple of days since the last run, no problem. I carry a spare lift pump, so can replace, and haven't yet checked out the start relay and its connections.

Am I overlooking anything?

[DmaxMaverick]

If it sat an unusual (for you) time, it's probably nothing more than some air in the fuel system. They bleed down after a while, and it's not unusual. If it starts normal, after a normal period, I wouldn't worry about it. If it continues, or gets worse when it shouldn't, look for a leak. Most likely the filter assy.

[rustyk]

Thanks for the tip on the filter. It only takes a few days (4-6) for the issue to occur, and it's sat far longer than that in the past without this issue.

I'm picking up a new lift pump relay tomorrow, and if I can find where it is on the motorhome, I'll replace it, as it seem more logical that's the culprit.

I'm glad it's not the lift pump, as I'd have to drop the generator fuel tank to get at it - when I do replace, it's getting moved to a more-accessible location :).

[rustyk]

Got the relay, but am going to have to trace the wires to see where it's located.

I decided to replace the lift pump, as this one has to be leaking back into the tank, meaning it may be getting weak. Got the coach up on the ramps and the waste tank drains removed, so I can drop the genset fuel tank out. Fortunately, I can remove and cap the lines before I move it - there's about 10-12 gallons of gaso in there...

As usual, there are a few "Mightswells" under there, too, so I'll deal with them.

[rustyk]

Epilogue: The lift pump was dead. I relocated the pump to the frame rail and added a jumper line to the engine compartment to run the pump to purge the air without running the engine.

Finish buttoning up the bottom (reinstall genset fuel tank and waste drain lines). Bleed the air and it's back in service. :D

[rustyk]

I got a bit cocky thinking the lift pump replacement would solve the issue.

I get a mist of diesel out of the exhaust before it starts reluctantly - after about a minute's total cranking.

The glow plug relay was replaced earlier with no change - I'm going to see if the glow plugs are actually getting juice - I'm beginning to believe they aren't. The injector return lines have been inspected and are intact. The drain and supply lines from the fuels fileter are as well. I also replaced the fuel filter and bled the system today...

Of course, any other suggestions, no matter how out-in-left-field (I always wondered why "left field" and not "right field" :D) are welcomed.

[rameye]

Did you get air in the pump during the pump change...wouldnt surprise me. If you have a crappy or no pattern due to air she wont light up too nice.

[rustyk]

I bled the system after the lift pump change. Then I had a 300 mile round trip, and the start for the return produced the usual nasty stuff.

Oddly enough, changing the fuel filter seems to have been the final cure. I've had three normal starts since then, once to go to the tire dealer for balance, once leaving, and a test this morning.

[rameye]

Maybe the dead pump put some junk in your trunk! (filter that is)

[rustyk]

Maybe the dead pump put some junk in your trunk! (filter that is)

:D Could have! Real test comes this Wednesday when I leave for near KC MO...it will have sat for five days...

[rapidoxidationman]

Have you tested all 8 glow plugs with an ohmmeter? How 'bout testing all 8 GP leads to make sure that juice is getting to them?

I've found on my '96 that I need to replace the glows about every 2 years... and if it is colder than 10*F it really would rather be plugged in for at least an hour before I try to fire it up.

[rustyk]

Update: I checked the "Start" position power to the lift pump, and it gets power.

I checked power to all the glow plugs (except #4 & #6 cylinder, which are buried inside the exhaust manifold). All got power, and the six I tested showed resistance.

However, I noticed that these were the 16 year-old plugs from my original engine - the spade terminals on #1, #2, and #3 were rusted to the female terminal - amazing they lasted as long as they did! I got a set of 8 AC60Gs from NAPA today, and will replace them tomorrow. One of the benefits of this engine being in a diesel pusher motorhome is that there's plenty of room to work; I should be able to access the plugs in #4 and #6 with a wobble extension, without removing the turbo.

I left it plugged in overnight at my sister's in NW MO prior to leaving, and it started with the usual protests at 25°F.

[rustyk]

Problem solved (maybe).

The new glow plugs made no difference - and the old ones had all checked good.

Reflecting back to when the problem first arose, I recalled it having started shortly after installing a new chassis battery; the other condition was that the problem started as the weather cooled.

The battery wasn't holding a charge well, so today I replaced it, charging it fully. This provided only a slight improvement, so something was still amiss.

Everything pointed to the plugs not getting hot enough (in a prior post I noted that I was getting a diesel mist out of the exhaust, so fuel apparently was not the issue.) Everything on the "hot" side of the glow plug circuit was fine, so it had to be in the ground.

So I disconnected the ground wires (3 of 'em - this is in a motorhome), and all, including the ground boss, were grungy. After cleaning them up and reconnecting, the glow plug light stays on about twice as long, and the engine fired right up after sitting 5 hours.

It looks as if the cause has been found. The grounds all attach to the bell housing, so one last project is to run a ground from there to the engine block.

Even though I chased down "dead" ends where the problem was concerned, the whole exercise was worth it because I found the dead lift pump (and relocated it to an accessible spot - now engine throttle response is noticeably better) and that the original plugs were still in there.

[rustyk]

Epilogue: It fired right up at 52°F last night and at 43°F this morning, without the block heater. Case closed - apparently!