hey guys i have an 87 with a 7.3 and i have been fighting fueling issues from the day i bought it. im sure many of you know it is supposed to have a 6.9 in her. it is supposed to have 60k on a rebuilt 7.3 that was swapped in. from day one she has missed and popped. i did compression test and all were great at about 475. i tested all injectors and glow plugs and ended up replacing them all. it still didnt run right. i found fuel pressure low so i put in a new lift pump. it runs okay at idle and mid throttle but anything after that it starts missing and cutting out and smoking white. i dont have anything to time it and either does anyone else i know. i was thinking either the injection pump its self was bad or the timing advance in the pump was bad. or timing which is cheaper but im having problems resourceing so i can check it. also i was wondering if anyone has blocked off the fuel pump and installed an electric fuel pump on these older trucks. let me know what you guys are thinking. thanks for any input!!!

 

87 came with a 7.3.........fuel pressure is 4-6 PSI.......

Sounds like it could be out of time.... possibly one tooth out. It could also be a stuck advance piston....

If you feel up to it ....do the check for Top Dead center for #1. If you line up harmonic balancer and check inside the IP/oil fill tower cover plate to see where the dowel is when all is aligned could help you find the problem. If it is out of time there is a simple fix........

The timing mark is found on a little plate that is on the front of the engine on the passenger side. The plate is mounted so it is very close to the main pulley on the lower front of the engine which is mounted on the vibration damper. On the side of the vibration damper, is a line, which when lined up with the line marked (O) on the plate, tells you that the #1 piston is at TDC(top dead center) You can see the line on the damper, and it points to the line on the plate with the (barely visible)O mark on it.You'll have to find a way to turn your engine over by hand (Crank/harmonic balancer bolt). Make sure you remove the power wire to the injection pump(so the engine won't start)and then rotate the engine until you can line up the marks.

The engine rotates in a clockwise direction as seen from the front of the truck, and for every 1/4 turn of the engine(crank) each next piston will arrive at TDC. So, When the line on the vibration damper is at the 2 oclock position, cylinders 2 and 5 will be at TDC. When the mark is at the 5 oclock position, cylinders 7 and 6 will be at TDC, 8 oclock has cylinders 3 and 8 at TDC, and back to 11oclock, 1 and 4 will be at TDC.

Cylinder numbers are assigned 1,3,5,7 on the right (passenger USA) bank from front of truck to back, and 2,4,6,8 on the driver's side (USA), front to back. Firing order is 1,2,7,3,4,5,6,8.

OK all the above is true...... to ensure the #1 piston is at TDC compression remove the inspection cover on the oil filler/gear cover. You will see a dowel pin from the IP if it is at 4 oclock that is TDC compression stroke, if it is at 11 oclock that is TDC exhaust stroke.......

Any other location then exactly at the two above positions would mean one of the 3 gears is out of alignment.

 

Super post except for the above. My `87 F250 has the stock 6.9.

 

according to my vin this truck did originally have a 6.9 and it is a 7.3 in there now sorry i thought all 87s had a 6.9 my stupidity of not checking that before i opened my mouth. when i was in tech school they had a special timing light that had a pulse sensor that clamped over the #1 injector line to fine tune the engine. i do know how to base time the engine i am lazy and was just trying to get some ideas before spring when i start working on it again. thank you for the great post though it is probably one of the most informative posts i have seen. once again thank you. i am running 6 psi fuel psi after my lift pump i was just bord pondering and thought an electric fuel pump would help the injector pump. if i remember right the injector pump pressurizes the pump case to like 140 psi and i thought if i had 60 psi going into the injector pump instead it would stress it less and it would pressurize faster.

 

60 PSI going to the IP would have the timing all messed up.

Part of what sets the timing advance is the fuel pressure in the IP housing.
If you supply higher pressure to the pump in the IP housing, the internal pump will just compound that pressure.

Top of the IP rotated toward the passenger side is advance on the timing.
Loosen the bolts and rotate the pump toward the passenger side about 1/16" and retighten the bolts.

When you get a rattle while the cold start timing advance is on, which then goes away once the high idle kicks off, you are where you want to be.

Never have the IP loose while the engine is running.
So this may take a couple days to get it set right since you have to run the engine untill it is hot and then wait till it is cold again before you can make the next try.

 

oh okay i was thinking for some reason that the throttle linkage on the side of the pump was what was engaging the timing advance. never mind that wouldnt work too well then would it. thanks for the info

 

On the ip bolts, a previous owner has partially rounded my PITA bolt. Is there any suggestions on how to get this one loose?

 

different tool companies even local parts stores sell a little socket kit that looks like sockets but they have grabber teeth in them that can grab rounded off bolts and thread them out. i cant remember cost though. i have a craftsmen set

 

The problem is the clearance room you have getting to the bolt. It takes a skinny wrench or one that is curved quite a bit

 

I don't think getting a socket on that bolt will be possible you might try grinding a 12 wrengh down maybe just maybe it will go on past the rounded part.
I have a ground down and even bent a little wrench that I use just cant get a wrench all the way on the nut.

 

if its the bottom bolt your talking about then thats a poblem. the only thing i can think of is the hard way and remove the pump and oil fill housing and cut the head off from the bottom side to get the pump separated from the oil fill housing then get whats left of the bolt out with pump off. but thats a hard way to do it maybe someone else has a good idea that isnt so much work.

 

If you have to remove the gear cover I would first follow PLC7.3 instructions to a T and make sure you get that gear back in the orginal place or you will open up a whole new can of worms.