7.3 cold start rough then rpms jump then stalls
#1
04-17-2014, 04:26 PM
7.3 cold start rough then rpms jump then stalls
so this morning i went outside to start up my 99 f250 7.3 psd and it was about 30-35 degrees and it took forever to get started i had not plugged it in but when it did start it was very rough then the rpms went up to about 1000 and then started to i guess you could say loping but not a good loping then stalled this happen the first 2 times it fired up but the 3rd time when the motor started to warm up it was alot smoother and back to normal this is really giving me a headache and cant seem to figure out why it does this if anyone has anything or if it happened to you and you fixed the problem please let me know thanks
#2
04-17-2014, 05:49 PM
Lead Driver
When it is cold, it is supposed to rev up to 1,000 RPM when idling and no one is touching the gas or brakes. There is a feature called the exhaust back pressure valve (EBPV). If the truck is left to idle and the engine oil temp is below 80 degrees (I believe) it will close and elevate to 1,000 or so RPM in order to load the engine so that it will warm up faster. If your truck is high idling because of the EBPV all you have to do is touch the brakes and it will come back down for a minute or so and then go back if the engine oil temp is still low. If touching the brake pedal doesn't "solve" it, then it is not the EBPV and something else is going on.
As for the hard starting and rough idle, there are a few things that can cause that. A bad glow plug relay, multiple failing glow plugs themselves, poor quality oil or long over due oil change, and finally worn injectors. If you have time, read my cold start thread in my signature. There is a lot of diagnosis help going on there and in my case, it ultimately was an injector issue.
As for the hard starting and rough idle, there are a few things that can cause that. A bad glow plug relay, multiple failing glow plugs themselves, poor quality oil or long over due oil change, and finally worn injectors. If you have time, read my cold start thread in my signature. There is a lot of diagnosis help going on there and in my case, it ultimately was an injector issue.
#3
04-17-2014, 08:24 PM
When it is cold, it is supposed to rev up to 1,000 RPM when idling and no one is touching the gas or brakes. There is a feature called the exhaust back pressure valve (EBPV). If the truck is left to idle and the engine oil temp is below 80 degrees (I believe) it will close and elevate to 1,000 or so RPM in order to load the engine so that it will warm up faster. If your truck is high idling because of the EBPV all you have to do is touch the brakes and it will come back down for a minute or so and then go back if the engine oil temp is still low. If touching the brake pedal doesn't "solve" it, then it is not the EBPV and something else is going on.
As for the hard starting and rough idle, there are a few things that can cause that. A bad glow plug relay, multiple failing glow plugs themselves, poor quality oil or long over due oil change, and finally worn injectors. If you have time, read my cold start thread in my signature. There is a lot of diagnosis help going on there and in my case, it ultimately was an injector issue.
As for the hard starting and rough idle, there are a few things that can cause that. A bad glow plug relay, multiple failing glow plugs themselves, poor quality oil or long over due oil change, and finally worn injectors. If you have time, read my cold start thread in my signature. There is a lot of diagnosis help going on there and in my case, it ultimately was an injector issue.
#4
04-17-2014, 11:00 PM
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To add to Jason's post, a failing Low-Pressure Oil Pump (LPOP) can cause a hard start/stall, then subsequent hard starts until running. Another possibility is an HPOP reservoir that drains down overnight and can't refill fast enough on initial start to fire the injectors properly.
You could check HPOP reservoir oil level before your first start in the morning. Just remove the Allen head plug atop the res. Oil should be about 3/4" from the top.
You could check HPOP reservoir oil level before your first start in the morning. Just remove the Allen head plug atop the res. Oil should be about 3/4" from the top.
#5
04-18-2014, 07:03 AM
Lead Driver
As the oil heats up and thins, it will run much better and you will feel like the truck is "as good as new" but as soon as the oil gets cold and thickens up again, like sitting over night in below 40 degree temps, you are back to a cold start problem. One relatively inexpensive and simple way to tell if it is injectors wearing out is to change the oil to synthetic 5w-40 oil. If that helps your cold start issues, then it is more than likely injector wear causing the problem. Synthetic oil is not a fix, you will be on borrowed time at that point.
However, I wouldn't jump to conclusions that it is the injectors just yet. I would first chech the glow plug relay and the glow plugs themselves first.
The buzzing noise you hear is more than likely a chattering relay which is a sign that you have low voltage. These truks use an electric solenoid on top of the injectors to make them work. They require 10.5 volts in order for the injector driver module to cause them to fire so you could potentially have enough voltage to turn the starter, but not enough to drive the injectors.
I would have your alternator and batteries load tested first, then check the glow plugs and glow plug relay, of course check the oil level in the HPOP reservoir like Tyler mentioned, in order to rule out a leak down situation and all this is assuming you have decent ol and a good level of it in the oil pan.
#6
04-18-2014, 09:35 PM
Yes. That is one of the signs that it could be injectors. Our trucks injectors are driven by high oil pressure. As the injectors wear, the tolerances on the poppet valve in the injector begin to make it harder and harder for the injector to do it's job when the oil is cold and thick.
As the oil heats up and thins, it will run much better and you will feel like the truck is "as good as new" but as soon as the oil gets cold and thickens up again, like sitting over night in below 40 degree temps, you are back to a cold start problem. One relatively inexpensive and simple way to tell if it is injectors wearing out is to change the oil to synthetic 5w-40 oil. If that helps your cold start issues, then it is more than likely injector wear causing the problem. Synthetic oil is not a fix, you will be on borrowed time at that point.
However, I wouldn't jump to conclusions that it is the injectors just yet. I would first chech the glow plug relay and the glow plugs themselves first.
The buzzing noise you hear is more than likely a chattering relay which is a sign that you have low voltage. These truks use an electric solenoid on top of the injectors to make them work. They require 10.5 volts in order for the injector driver module to cause them to fire so you could potentially have enough voltage to turn the starter, but not enough to drive the injectors.
I would have your alternator and batteries load tested first, then check the glow plugs and glow plug relay, of course check the oil level in the HPOP reservoir like Tyler mentioned, in order to rule out a leak down situation and all this is assuming you have decent ol and a good level of it in the oil pan.
As the oil heats up and thins, it will run much better and you will feel like the truck is "as good as new" but as soon as the oil gets cold and thickens up again, like sitting over night in below 40 degree temps, you are back to a cold start problem. One relatively inexpensive and simple way to tell if it is injectors wearing out is to change the oil to synthetic 5w-40 oil. If that helps your cold start issues, then it is more than likely injector wear causing the problem. Synthetic oil is not a fix, you will be on borrowed time at that point.
However, I wouldn't jump to conclusions that it is the injectors just yet. I would first chech the glow plug relay and the glow plugs themselves first.
The buzzing noise you hear is more than likely a chattering relay which is a sign that you have low voltage. These truks use an electric solenoid on top of the injectors to make them work. They require 10.5 volts in order for the injector driver module to cause them to fire so you could potentially have enough voltage to turn the starter, but not enough to drive the injectors.
I would have your alternator and batteries load tested first, then check the glow plugs and glow plug relay, of course check the oil level in the HPOP reservoir like Tyler mentioned, in order to rule out a leak down situation and all this is assuming you have decent ol and a good level of it in the oil pan.
#7
04-19-2014, 11:34 AM
Lead Driver
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