'94 E-350 7.3L IDI cold start problems HELP!
I know this is a little long, but I and the mechanic are stumped, I need some help figuring this out, and I NEED my work vehicle, so I'm giving you the entire rundown.
I own a locksmith shop & bought an ambulance to use as a service vehicle. Having worked as a mechanic years ago, I have a basic understanding of the workings of a diesel, though far from thoroughly knowledgable. I have a '94 E-350 7.3L IDI 150,000 miles or so, starts great whether or not block heater has been plugged in unless it's been sitting more than a day. If I don't go out & start it & run for 5 minutes or so each day, I have a real difficult time starting it.
I'll let it sit over the weekend without starting it, all the while block heater plugged in & heating just fine. When I go to start it Monday morning w/ warm engine (from block heater), I crank & crank, but no start.
It had this same problem several months ago. My mechanic suggested I hold the accelerator to the floor & crank for up to 30 seconds at a time & see if it starts. If not let it sit for 15-30 minutes to give starter time to cool. Started next few days within 2 tries, so I took it in & my mechanic found a pinhole leak @ the fuel heater & replaced it. We surmised pinhole leak was allowing gravity to slowly draw the fuel back down into the tank over time & constant cranking @ full throttle would allow mechanical fuel pump to pull fuel back up after several seconds. He replaced the heater assembly, injector O-rings, and 4 glow plugs (used Autolite plugs) & it started fine.
About 4 months later, I began having start problems again & glow plug lamp lit for just a few secs, then started blinking. Time to replace more bad glow plugs.
Frustrated w/ the start problems & not knowing when GP controller had last been replaced (I bought the van @ 98K miles), I decided to make sure I was covering all the bases & hopefully saving further future hassle. I went to the Ford dealer & bought new Motorcraft gp controller & all new Motorcraft glow plugs (Motorcraft Wrapper, but Beru label on the plugs). I changed them all out, careful to use a vacuum cleaner at each glow plug hole before and as I was removing the old plugs so as not to get any trash in the cylinders. Put it all back together & glow plug controller lamp lit for approx. 30 secs & she fired up like a champ. Hallelujah! Now I'm good to go, right?
3 weeks later, 1 battery gave it up, so I went to Interstate & replaced all 3 batteries (950 CCA each = 2850 total, turns over quickly). That did it, started like a champ once more. No problems for the next 2 months.
Now I'm having same problem as before when fuel heater had pinhole leak. I didn't check the glow plugs as GP controller lamp still stays on for 30 secs or so and van starts fine as long as it hasn't been sitting for more than about 36 hours. Hot/warm starts are no problem either. In fact when it's warm & has been running in the last 24-36 hours it starts immediately on cranking as quickly as any gas vehicle.
If it's been sitting for more than a day though, I have to crank & crank while holding the accelerator to the floor, until it eventually starts.
I've also checked the 200 amp Leece-Neville alternator & it's charging just fine & those 950 CCA batteries all test @ 1110 - 1120 CCA. Batteries & charging system are no problem.
My mechanic is the best diagnostic guy in all of the Richmond, VA metro area....on gasoline vehicles. Diesels are not his specialty, but he does pretty well overall & I trust him. He just hasn't serviced enough diesels on a regular basis to have attained the troubleshooting & diagnostic prowess he has with gas engines. I'd rather not take it elsewhere unless I have no other option. Most diesel shops see you coming & bust you wide open (especially when they see the ambulance). The few I've tried have been less than what I would consider professional & leave me with a less than trustworthy impression.
I'm not sure these have anything to do with my problem, but I'll mention them:
1. In a hurry, 1,000 miles overdue on my oil change already, no time in sight to do it myself, I stopped at Walmart next door to the job I was on to have it done. I know, I know, Walmart is typically a bunch of hacks, but I talked to the 2 "mechanics / oil change fellas" before I let them do the job. These guys were mid to late 30's, not young punks and knew my engine took 10-11 quarts of Rotella 15W40, so I felt like they were capable enough. I wasn't excited about the Fram filter but it'll work. I checked the oil before I left, level was good, no milky color (as if coolant were getting in). After 1,000 miles now, level is still good & oil looks fine.
2. About 3 years ago, I installed a toggle switch on the console to break the power to the coil of the GP relay. I leave it on most all the time. I do turn it off for hot starts only.
Any tips / pointers etc would be greatly appreciated.