Here are a few questions that are puzzling me

Oil pressure gauge dropped today, it is still in the normal range but it is bouncing around a bit. Could it be, the cold weather/cold weather hitting the front of the truck, plus a really foggy day out today. I did wrap up the front end with the winter front. Truck sounds the same, gauge doesn't drop right off. Any help here please.

Glow plug cycle.

Is it ok to cycle the glow plugs twice to start my truck, it is cold up here, today -10 C and the truck isn't pluged in.

 

I've noticed the same thing with my oil pressure gauge. I've been told that it's not a true pressure gauge and that it's just indicating that you have oil pressure but not at a specific amount. Nothing to worry about there. As far as cycling the glow plugs it isn't a problem at all. They'll charge for up to 2 minutes when it's cold so just turn the key and wait. You should notice a drop in your ammeter showing that they cycle on and you can watch it jump when the system cycles back off. If you want to run it through again you can but if they're working properly then 1/2 minute should be more than enough to get the motor to fire. Plugging it in for a couple of hours does help with getting the engine warmed up quicker so it's nice to do it when you can.

 

Hey Chapguy,

You have answered another question I had awhile ago, so Thanks.

Glow plugs, I have tried to start it with the first cycle but no go, then I tried to start it after a second go round and the beast fired right up. I do plug it in over night and the good ol girl fires up on the first crank around.

So you say that the idiot gauge reading doesn't mean alot but it does concern me, as I said, does the cold weather affect it as the deisel is a slow heat producer.

 

I have driven these trucks on the north slope at -40F and 40 mph winds and the gauges never bounce.

 

never heard of one bouncing... maybe your sending unit is on the outs???????

its true that they are not a true oil pressure gauge.
cycle the glowplugs as many times as it takes it wont hurt a thing.

 

Just FYI. The length of time the "wait to start" light stays on does not indicate how long the glow plugs are on. The WTS light is controlled independently of the glow plugs by the PCM. I beleive the max time the WTS light will stay on is 10 seconds. The max time the glow plugs will stay on is 120 seconds. One of the true indicators of when your glow plugs turn off is when your volt meter goes from a low reading to a normal reading after the truck is started. The glow plugs being "on" draws a lot of current that shows up on your volt meter. You can cycle them off and on if you want or just not crank it right away after the WTS light goes out to give the glow plugs some additional time to warm the cyclinders.

 

I also heard that the glow plug logic was different- upgraded on the newer ECMs (1996) compaired to the 94.5. Anybody know what got changed or if it works better in the later models?

 

sorry- ment PCM

 

FyI, Guys, I dont mean its bouncing all around, I just meant that the gauge has been rising and falling more than normal but still in the "normal" range.

I'll try the "dont crank" right after the WTS light goes out and wait just a bit longer to fire it up on the really cold days.

 

The oil pressure sending unit is pretty much just a switch as I understand it. At 7 psi (I think that's the right value) it "switches" and "turns on" the oil pressure gauge. It's pretty much an all or nothing set up. As long as you have 7 psi of oil pressure, your gauge will read "normal", wherever the needle ends up.

As far as the "bouncing", it might be due to the cold weather. As I understand it there is a resistor in the gauge circuit that may be impacted by the cold causing the needle to fluxuate, but that's just a guess. If it does it with the cab nice and warm, I'd guess it's the gauge and probably not worth worrying about, because I think you have to replace the whole gauge cluster to fix it. Think big $$$ for a idiot gauge. You'd be better off installing a real oil pressure gauge somewhere.

Here's some info from Steve Baz site on how to change the "95 and "96 gauges to read real oil pressure. Us '97s are out of luck.

Real Oil Pressure Gauge For My Dash? 95 & 96 Only
To make your oil pressure gauge show real pressure, follow these steps: remove gauge cluster by prying out horizontal trim strips and removing the TX20 screws underneath, pull forward on trim panel and disconnect tank switch and warning lamp module. Remove the 4 TX20 screws at the corners of gauge unit and disconnect (by pinching on both ends) the two large connectors and also the small speedometer connector. Gauge has to be turned 90 degrees to undo connectors and to remove it, watch out so as to not scratch face of gauge set. Lay gauge unit on a flat surface gauges down and locate the 20 ohm resistor (it's marked). Solder a jumper wire across the resistor using a pencil solder iron so as to not melt your circuit film. Reinstall cluster and all trim. Remove the top engine cover assembly by undoing the three 13 mm cap nuts. The oil pressure switch is on the front aluminum housing under the removed cover and has a single slide-on wire connector. Remove this switch. Fit an oil pressure sender (sender from a 1980 F150 with 400 cu. in. engine is correct) using two short 1/4 NPT nipples, one 1/4 NPT 90 elbow, and one 1/4 NPT female connector. Fit one nipple into the hole, screw on elbow, screw in the other nipple, and screw on the connector. Orient fitting so that it points at the driver's seat so as to allow clearance for sender to not interfere with fuel system sensor that is immediately behind hole where fittings are installed. Screw in sender and plug on wire. Use Teflon tape or other pipe sealant at all threads. Re-install your top cover. Oil pressure gauge seems to read 0-90 psi according to my testing. Strangely enough, when engine is hot and cruising the gauge reads where it did with the "liar" setup, but it does read higher cold and lower idling.

 

Thanks Stroker2
I have Baz as a Bookmark, great site, Ive tried to email him and he didnt get back to me. Thanks guys