Yet Another Hard Start

[RJMorrow]

I have a '95 F-250 7.3L which has become increasingly hard to start. This is a problem in any weather less than 60 degrees. I have checked my GP resistance and all are good, also verified GP relay operation. The truck does have a block heater which i replaced the cord end on and tried but did not really help (verified block heater element resistance, ok).
I am still learning about these diesels, but i suspect i am not acheiving the necessary RPMs to start. In addition, i only get about 15-20 seconds of crank time before batterys give out. I have replaced one battery so far and i load tested the remaining battery and it appeared ok. The truck runs fine once started and will start with a booster/charger assistance. At this point there are 298,000 miles on the truck and I do not have extensive service history from previous owner.
Both batterys read good voltage after sitting idle for several days.

My suspicions are bad starter/battery cables or a bad starter. Does anyone have a ballpark figure for starter current draw during starting?
Or any suggestions on where to look next ?
Is there a neccesary RPM that must be achieved in order to start?


Thanks,
RJM

 

[NJKen]

The most likely cause is the glow plug relay. They can have voltage to them but not close when enrgized. You can test it with a simple meter or even a test light by going between the 2 big terminals. If you use a meter you should see about 12 volts or your test light will light. Have someone turn the key on but not crank the engine and the meter should drop to near 0 volts or the test light go out. Re-post with your findings.
Ken

 

[69oiler]

as a rule you should replace both batteries at the same time. just because they show good volgate does not mean the have good amperage.

i'd guess weak batts or maybe weak starter. possible batt cables if they show signs of corrosion or overheating. the truck should not need a block heater or glow plugs to start at 60 degrees.

 

[RJMorrow]

I did verify GP relay operation prior to posting. Also, I used a load box to test the batterys, not a voltage measurement. I was just stating that I had monitored the battery voltage over a several day period to make sure it wasnt falling off due to dome lights, glove box lights or some other acc.

Any ideas on expected starter current draw?

RJMorrow

 

[NJKen]

Starter draw is between 350 and 600 amps depending on temp. Inrush could exceed 3000 amps (measured with a Fluke 337 meter)
Glow plug draw on the powerstroke is between 100 and 200 amps.
When she cranks are you seeing any smoke at all? The glow plug relay can work when it feels likeit and not when it feels like it. I had this intermitent no start on my 02 because of that darn thing.
Ken

 

[Mike]

How many miles on the engine? When was last oil change? How old are your batteries? I'm suspecting batteries here. Even if it sounds like she is wheeling over properly you might not have the umph there needed.

 

[RJMorrow]

Engine miles is 298,000 . Last oil change was about 1200 miles ago. One battery is effectively brand new Interstate, the other is several years old. The older battery did load test well, but this could be misleading. At this point I believe the glow plug relay is working correctly.

 

[Papabear]

I have always been told that if i am going to swap any multiple battery configuration from dual batteries in a pickup all the way up to a 24volt setup on equipment to swap out all batteries at the same time because one bad cell can bring the wholething down and damage the other batteries.

 

[Mike]

Change the second battery.