Hard Start, Runs Rough...Sometimes - CPS? Or? - Diesel Forum - TheDieselStop.com
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99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the 99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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Old 11-03-2012, 09:23 PM   #1 (permalink)
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Hard Start, Runs Rough...Sometimes - CPS? Or?

I've had the truck a few years now, and am still not 100% familiar with the engine or the fact that it runs diesel. Don't get me wrong, I LOVE that its a diesel, and I'm proud as hell that I've got the 7.3L that everyone loves, just wish I had the time and knowledge to know this thing inside out. Here's my issue.

The truck has always been tough starting on cold days, checked the gpr, and the glow plugs, all seemed to test out fine so I chalked it up to being tough starting in the cold - 30F and colder. Everyone I've talked says that the 7.3 is a little cold-blooded.

It's gotten tougher to start lately, seems like it cranks forever. I replaced both batteries, no change. A couple weeks later just about ran out of fuel, chugged along to the station, made it, but it has run rough since. I know, bad on me, fuel gauge doesn't work so I set my trip-meter and didn't realize I was low.

Since then, most of the time it runs rough, sometimes it doesn't. No loss of power, just shakes a little at idle and sounds like hell at speed. Hasn't ever stalled. Figured I picked up some garbage or air since I let the fuel get low, but the problem hasn't solved itself! It is getting fuel, filter is clean, I haven't checked the pressure of the fuel or oil.

Drained a little fuel from the fuel bowl, seemed to run a little better, but didn't go far with it. Just went out and tried to start it after reading a post, and it stilled cranked long and hard, took two tries to start. A side note - as I was draining the fuel, I noticed that there is a wiring harness plug-in on the back of the fuel bowl. The plug-in was un-plugged and wrapped in saran wrap and zip-tied. What's up with this? Shouldn't it be plugged in, is there a good reason why it's not? Anyone heard anything about this?

That said, I read an article on a failed CPS and it said that one of the tell-tale signs is either it won't start at all or takes a long time to crank, then start. Noticed that it doesn't register RPMs until it actually does start, while cranking it doesn't show up. Could the CPS be the answer I've been trying to find?

Thanks in advance for the help, I really appreciate it, and appreciate the patience as I'm practically a diesel engine "virgin" - just happy to be part of the family.

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Old 11-03-2012, 09:35 PM   #2 (permalink)
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Yea, a bad CPS will cause a REALLY long crank till the batteries are dead. If you're getting white smoke and tech is moving (only on 99-01) then CPS is good. Plug is probably fuel bowl heater.

Check fuel pressure. Does it run better above 1/4 tank? How old is oil and what weight? Does it start better with block heater being plugged in? Really a lot of things to check....start simple and work you're way up. Oh...where is the hpop reservoir level before you crank?

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Old 11-03-2012, 09:55 PM   #3 (permalink)
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Always cranks long, I don't ever crank for more than probably 10-15 seconds because I've been told much longer could damage the starter.
Always starts up with a little puff of dark smoke (certainly not white) but clears up within seconds. Tach doesn't move an inch when I crank, just checked.
I assumed it was for the fuel bowl heater, should it be plugged in, wouldn't this make it start a little easier in the winter. Any good reason why it isn't plugged in?
I changed the oil about 14 months ago, certainly doesn't have 3,000 miles on it, and I don't let it idle all day like some guys do so it shouldn't have many hours on it either. It is the weight that was recommended in the diesel supplement in the ford manual, I don't honestly remember what weight specifically but it was correct, and it was diesel specific with the proper certifications. Plan to change it soon, I like to change it at least once a year regardless of mileage, unless the mileage creeps up first.
I haven't plugged it in recently so I'm not sure if that would decrease the start time. Before this headache, I plugged it in during the winter and it always started perfectly, but if it wasn't plugged in, min. of 1hr it would start hard or not at all. When it did start, and wasn't warmed up it ran rough, but a different kind of rough than this.
Going to put more fuel in it tomorrow. I'll check the hpop reservoir - where is it and what am I looking for?!
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Old 11-03-2012, 10:05 PM   #4 (permalink)
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Quote:
Originally Posted by duprat_design View Post
Always cranks long, I don't ever crank for more than probably 10-15 seconds because I've been told much longer could damage the starter.
Always starts up with a little puff of dark smoke (certainly not white) but clears up within seconds. Tach doesn't move an inch when I crank, just checked.
I assumed it was for the fuel bowl heater, should it be plugged in, wouldn't this make it start a little easier in the winter. Any good reason why it isn't plugged in?
I changed the oil about 14 months ago, certainly doesn't have 3,000 miles on it, and I don't let it idle all day like some guys do so it shouldn't have many hours on it either. It is the weight that was recommended in the diesel supplement in the ford manual, I don't honestly remember what weight specifically but it was correct, and it was diesel specific with the proper certifications. Plan to change it soon, I like to change it at least once a year regardless of mileage, unless the mileage creeps up first.
I haven't plugged it in recently so I'm not sure if that would decrease the start time. Before this headache, I plugged it in during the winter and it always started perfectly, but if it wasn't plugged in, min. of 1hr it would start hard or not at all. When it did start, and wasn't warmed up it ran rough, but a different kind of rough than this.
Going to put more fuel in it tomorrow. I'll check the hpop reservoir - where is it and what am I looking for?!
Your starter could also be weak or not have a good connection. I also recommend trying to start after the gpr goes off. What model is the truck? You can't gauge the cps operation by the tech if its an 02-03.

Wow, that's a long time on a oil change. A diesel needs to be driven or at least cranked time to time. 15-40 is what is recommended. Some people switch to a thinner/synthetic oil for winter. Its hard for cold oil to flow through the lines until it gets warmed up a little.

HPOP reservoir is the flask looking container in front of the fuel bowl. Open up the top plug and you're checking for oil level...forget what its suppose to be. If its draining down, it will take longer to get the truck started.



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Old 11-03-2012, 10:25 PM   #5 (permalink)
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The truck is a 99 F350 srw.
I'll check the hpop tomorrow. Do I check it before cranking or during, or both?
To try starting after the gpr goes off do I just wait for the "wait to start" light goes out? If so, that's what I've always done.
I drive the truck just about daily, I just don't drive far. I'll change the oil more frequently if that's what I should be doing. The dealership told me it would be fine, based on my limited mileage if I change it yearly. If more frequently is recommended I'll certainly do it.
A weak starter wouldn't have anything to do with it running rough, right? Just maybe slow starting.
Back to the cps, if my truck is a 99 should the tach register as I try and start, or am I just reading into things too much?
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Old 11-04-2012, 07:52 AM   #6 (permalink)
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Well at least we can rule out spark plugs . Diesels are great but if you own one sooner or later you are either in a place where you have to learn about them and do DIY work or pay someone that does, like a dealership or professional mechanic. Better to learn somthing about them so that when you take it to the dealer or mechanic you are not totally at their mercy.
Your truck, while I wouldn't go to the store a 1/2 mile from my house without a spare CPS, yours doesn't sound like a CPS, but get one anyway and put it in the truck for a spare, less than 30 bucks now they are cheap. Change your fuel filter, clean out the fuel filter reservoir if it has crud in it. Put a 4" long piece of 5/16" dia fuel hose on the end of the filter reservoir drain. Pressurize the fuel system with a couple of key on cycles but don't start the truck up. Open the fuel filter drain and put the end of the hose into a container. Turn on the key, or get someone to, and watch the fuel come out into the container. It should be a full stream. In the 10 second cycle it should pump about 16 ounces, anyway not a dribble. If that is good then you have established fuel flow. It is OK to put the fuel back into the tank.
If you have good flow then check your batteries, they both need to be good, not one bad one and one new one. They can make a big difference in starting cold ambient or hot. Get the basics down, fuel and batteries. Plan on fixing your fuel level indication, probably an inside the tank problem. Good Luk 106
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Old 11-04-2012, 05:14 PM   #7 (permalink)
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Quote:
Originally Posted by duprat_design View Post
I'll check the hpop tomorrow. Do I check it before cranking or during, or both?
DON'T try cranking with the HPOP reservoir plug out, unless you want to reenact an Oklahoma oil gusher.

Check out your GP system, and also check the battery cable connections. Bad connections can cause lower voltage getting to the starter and slower cranking.

Check the Hard/No Start link in my signature for GP checking. The GPR is active for up to 2 minutes depending on outside temperature. So it can be on for quite a bit longer than the WTS light, which is independent of GPR operation.

There's a possibility that you got some dirty fuel after running that low, and some crud from the bottom of the tank got stirred up and wound up in the pickup screens in the tank. That might be the cause of your rough running.

And the unplugged fuel heater doesn't really affect starting. If you live in real cold country (you mentioned -30F), I'd get it fixed though. It's there to help prevent fuel gelling in the housing and plugging the filter.
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Last edited by klhansen; 11-04-2012 at 05:19 PM.
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