F250 7.3L Diesel starting quirk

[RoyKing]

It will be the relay, his truck has very low mileage but lots of years, plus the completely dead, then perfect is the relay symptom and it throws no codes. We will know soon as gets a chance to swap the relays

 

[jmc]

OP here. I know that cranking rpm is critical because I replaced the batteries once before and it started fine afterward, even though the old set still cranked (seemingly) ok. It starts now after cleaning all the cable terminals and I'm waiting for foggy weather for the real test. Terminals weren't fully corroded, but a little chalky.

Also, Langanobob mentioned his glow plugs draw the voltage down to about 8 volts when the engine is cold. My voltage drops only slightly, maybe 10. Hard to put a number on it since there's only 8 and 18v calibrations, but it's well above 8v.

It's supposed to be warm and wet again later this week.

Thanks, All.

 

[SPYDERLK]

Sounds like you are partially losing prime on your injector pump. Otherwise it would smoke a bunch when starting after extended cranking.

A tiny crack in a suction line. Temperature affected. Check valve? :confused3:​

 

[RoyKing]

Everything mentioned would give you smoke when it starts, I needlessly replaced batteries also, next time no start swap relay

 

[jmc]

OP here again.

53F today and raining; similar to the warm, wet day it wouldn't start before. Starts OK today, but it still had to crank awhile. Although both batteries were new several years ago, I'm taking it back to have them tested under load, as another poster suggested. Previously, when it wouldn't fire, the batteries seemed to poop out early. If that's not it, I'll wade into the relay suggestion. Thanks, All.

 

[terryknight]

are you getting smoke from the exhaust while you are cranking before it starts? it really sounds like weak batteries and gp issues

 

[Langanobob]

Not to disparage any of the advice you’ve received here, but there are OBS 7.3 Ford forums populated by a bunch of guys who troubleshoot these things all day long. You might try checking in at one of the Ford truck forums

1994.5 - 1997 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums

OP here again.

53F today and raining; similar to the warm, wet day it wouldn't start before. Starts OK today, but it still had to crank awhile. Although both batteries were new several years ago, I'm taking it back to have them tested under load, as another poster suggested. Previously, when it wouldn't fire, the batteries seemed to poop out early. If that's not it, I'll wade into the relay suggestion. Thanks, All.

 

[RoyKing]

OP I thought batteries as slow crank speeds, but new bats didn't fix it, cleaning connects didn't help. The starters on these trucks just slow down and finally quit, slow crank also leads to slow start. But turns out that has nothing to do with crank but won't start and no smoke or error codes that's the relay, next odd one is no cab fan and few other things like dash lights, that the ignition switch in the column real easy fix one screw, one plug.
I have same year truck f350 7.3 4x4 crewcab 83,000 miles. Erratic over drive and speedo is speed sensor rear axle, abs break light is Ford make sensor leads too short on front axle and they fail. All cheap except starter, shop around big difference on prices from $180 to 380, I got new but different brand with life time warranty.

 

[RoyKing]

Not to disparage any of the advice you’ve received here, but there are OBS 7.3 Ford forums populated by a bunch of guys who troubleshoot these things all day long. You might try checking in at one of the Ford truck forums

1994.5 - 1997 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums

That right place buy you want 1999-2005 7.3 section, between the forum, YouTube, and shop manuals I figured all mine out.

 

[Langanobob]

Roy, you are right about 1999, for some reason I was thinking it was a 1997.