p0703 and p0087 - Ford Powerstroke Diesel Forum
6.4L Performance Parts Discussion What has or has not worked for you?

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  #1  
Old 06-19-2010, 07:52 PM
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Unhappy p0703 and p0087

I updated my mini maxx to the 6.4.11 hot damn Wednesday night and all was well. The tranny relearn was also done. This afternoon I noticed the truck was surging at idle. The rail pressure is bouncing between 4100 and 5500 at idle on all tunes. It used to be at 5800. While runing the throttle response is fine but at a stedy cruise the rail presure bounces 4-500 psi. I went on a 200 mile trip tonight and pulled the p0703 brake switch B circuit and the p0087 fuel rail/system pressure too low. The truck at idle feels like it wants to stall, and the cruise control doesn't work. My fuel filter only has 3000 miles on it. I am running the stock intake and exhaust. I have only run the Hot Damn tune 6 or 7 times and always run the mild tune around town and on the interstate. Ths is the first issue I've had with the truck. The truck has been tuned for 4000 miles and has 102,000 miles on it now. My dealer is not mod friendly and the diesel tech is not real friendly.
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Old 06-19-2010, 08:17 PM
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Have you cleared the codes yet? I would clear them and see which ones come back. You may have a High Pressure Fuel Pump problem. They are quite common on the 6.4s. If you clear them, does the Idle smoothen up? Does it run ok otherwise, or is it in a "limp mode".
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Old 06-19-2010, 08:22 PM
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I cleared the codes and the p0087 went away and the idle smoothed out but the rail pressure is still only at 5100-5200. The p0703 is back though. any ideas on the p0703 code. Thanks for the quick response.
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Old 06-19-2010, 08:54 PM
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P0087 would be the only code related to your issues with the rail pressure. I got that code when my high pressure fuel pump went out. The P0703 is a brake switch code.
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Old 06-19-2010, 10:43 PM
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Your cruise wont work with the p0703 present. Take it to the dealer and have the brake switch replaced. Should fix the problem. I had the same thing but I believe they had to replace part of the cruise control module to get it to work.
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Old 06-20-2010, 04:52 AM
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Thanks guys. I was afraid the HPFP might be going when I got the code. Does anyone know what it cost to replace the HPFP?
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Old 06-20-2010, 07:47 AM
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How hard were you running it when you got the 0087 code? did you do a few WOT runs in a row?

I have seen a couple trucks running the HOT DAMN tuning that throw the code and limp mode the truck until they clear codes. Some HPFPs are just a hair weaker than others and will pop that code early. The pump will probably last you quite some time longer, but may not give you the full power potential.

Pumps can be bought for about $800, but the labor is pretty intensive. It is also recommended to replace all fuel lines, washers, gaskets, etc. while you are in there. Its a lot of work and not fun when you put it back together and something leaks..... Not sure what a shop would charge for this, i would guess $1000 in labor.
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Old 06-20-2010, 09:18 AM
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When you say stock exhaust, do you still have the DPF on?
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Old 06-20-2010, 10:29 AM
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Quote:
Originally Posted by MississippiJoe View Post
When you say stock exhaust, do you still have the DPF on?
I kind of wondered the same.... but I believe he meant "I am running stock intake and an exhaust". hopefully that is what he meant! if not, get that stock exhaust off of there!
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Old 06-20-2010, 12:03 PM
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Stock exhaust no DPF. I've put about 4000 miles on the truck with the mini maxx and this is the first issue. I did one run with the hot damn tune from 70 to about 110 (to keep the tailgaters honest) and that was it. I have ran nothing but the 80 hp tune for the last two weeks. I run the 80 pretty hard but niether of the codes thru the SES light nor did the truck go into limp mode. I ran the truck today for about 100 miles on the 80 tune and all is well no DTCs. I did run the truck way low on fuel last night before my trip so maybe some air got into the system and after cycling the key a few times it worked it's
way out. As for the p0703 code that's gone also. I'm at a loss but I love running the truck with the H&S tunes. I've got another 300 miles till I'm home and I update you guys. Thanks again.
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