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Discussion Starter #1
Hi folks,
I have a 95’ f250 7.3 and it has difficulty starting after sitting out overnight. Seems like a low fuel pressure issue — regardless of tank selection, if I prime the system (turn key 4x to pos 2/wait to start, wait 15 sec per fuel pump prime) it fires right up. Runs and drives fine once started. I dropped the front tank and replaced the strainer, plus replaced the fuel filter recently.

What else can cause low fuel pressure? I know there’s a strainer on the FPR, but I don’t think that’s the issue. The primary fuel filter that I removed was clean, plus the fuel tank was clean, just missing the strainer.

Perhaps glow plugs? I think the previous owner did them less than 100k ago
 

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Is this truck stock or has it been modified to have an electric fuel system? If stock it only has a mechanical pump (cam-driven in the valley of the motor) so it will not prime with the key in WTS (engine has to be turning to pump fuel). Start off by seeing what the fuel pressure is when cranking. It should be a minimum of 25 psi at 100 rpm minimum crank speed. You can use a "stick-type" tire pressure gauge on the shrader valve (just use a rag around the joint to avoid getting sprayed with fuel). As far as glowplugs, are you getting white smoke when cranking? Note that the WTS light has nothing to do with when the plugs are active. The glowplugs will be active for up to 2 minutes after the Key is turned to WTS. Also, cycling the key doesn't do anything other than wear the key cylinder. Try waiting an additional 30 seconds (or more) after the WTS light goes out and then try to start it. Cheers!
 

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Discussion Starter #3
First off — huge THANK YOU, Patrick. Had no idea the fuel pump was mechanical and cam driven only. That changes everything. This truck is bone stock, no mods, just 300k mi and a buncha maintenance done by me recently.

Yes, when it is really having difficulty starting, it puts out white smoke once it eventually starts, then goes away shortly afterward. I assume that means I’m having a glow plug problem? Or if not, something really involved to fix?
 

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Sounds like glow plugs. You can check or replace the glow plug relay and see if that solves it.

If the glow plugs are original or condition is unknown then it might be best to replace them and the UVCH and valve cover gasket for each side. Replace it all while you are under there. It'a been about 6+ years since i've been under my valve covers since I replaced everything at once.
 

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Here are some testing procedures I use:

For checking the injector/glowplug wiring: From each valvecover gasket connection's outermost pins (2 per connector) to ground you should get 0.1 to 2 ohms (indicates good plug and wiring). From each valvecover gasket connection's center pin to each immediately adjacent pin, you should get around 3 ohms (indicates good injector solenoid and wiring). You should not get any continuity from any of the outer pins to the 3 inner pins (indicates no shorts between injector and glowplug wiring). You should also get 0 to 1 ohms from each of the external harness connectors outer pins back to the Glowplug Relay's large terminal on the GP side (indicates good wiring from external connections back to the relay).

To check the glowplug relay (GPR), measure the voltage drop across the GPR's large terminals. While the GPR is active (up to 1.5 to 2 minutes after the key is turned to Wait-to-Start) put your meter leads on the large terminals (one lead on one large terminal and the other lead on the other large terminal). The measures how much voltage is being "lost" across the relay. A reading of 0.3V or more indicates a bad relay. Also, check the relay’s control wires (smaller wires) disconnected from the relay for battery voltage at the Red/Light Green striped wire and ground at the Purple/Orange striped wire (check both when the key is turned to Wait-to-Start).

Cheers!
 

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Discussion Starter #6 (Edited)
Either I’m spot on, or totally off base here. I did the glow plug relay test, but there’s battery voltage/12.57 v across the two large lugs on the relay. It’s present regardless of in WTS position or not. Supposedly, one of the large lugs always has 12v, then when in WTS the opposite lug gets 12v... mine definitely doesn’t do this. Safe to assume that I have 12v or loss across the relay and that this thing is dead?

And, Thx to Pat, I tried leaving the key in Pos 2 for a minute or so this morning. Fired on the first try!
 

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It sounds like your relay is bad based on those numbers. If you do get a replacement I'll recommend getting a White-Rogers (formerly Stancor) 586-902 at $50-$60 (it's been a long time since I bought one) or a Western Plow 56131K at about $20. I've used both with complete success. I had the W-R on my 94 and the Western Plow currently on my 97. The Western Plow fits better on my due to the shunt used for glowplug monitoring on the California 97s. Cheers!
 

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Discussion Starter #8
If my relay has 12v of loss, doesn’t that mean it’s totally dead?
If that’s the case, why does leaving the key in pos 2 for a minute help startup?
 

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Normally the relay contacts are supposed to rotate a little to avoid wearing/burning in a particular spot. If it is on a dead spot the relay doesn't work, if its on a good spot it works (that would be my guess if you did the drop test correctly … plugs active). Make sure you do the control wire test in my other post to make sure that the control power is there and that the PCM is providing the ground to complete the circuit before condemning the relay! Cheers!
 

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Discussion Starter #10
I did the control wire test, but didn’t disconnect the wires. The relay looks pretty icky — the rubber boot on the always hot wire literally came apart in chunks when trying to pull it back....
 

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Do you have the old style relay with the Weatherpack connector for the control wires? If so, just get rid of that relay as it is probably toast (literally). Almost any new relay, you will need to extend the control wires a little and put ring terminals on the ends. Ford originally had a kit that had a new relay (all 4 ring terminals, 2 big and 2 small) and a pigtail adapter that converted the original harness connector out to ring terminals. Cheers!
 

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You already have the "updated kit" as I described then. I would still probably opt for the White Rogers relay since it looks like your relay is bad. The little pigtail just makes it easier to use other relays since there is no extending/splicing involved. Cheers!
 

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Discussion Starter #14
Is there any possibility of wiring this wrong? My White Rogers is coming in a few hrs. Is the WR relay identical to the Ford one, just bigger.
 

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It will mount a little differently (no big deal), but the wires just go big-to-big and small-to-small! No way to really mess it up. Unhook your batteries when installing it. Cheers!
 

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Discussion Starter #16
Installed the aforementioned White Rogers relay. Bit of a pain because it’s not the same size/shape as stock, but did drop in without mod. Preliminary results are promising. Truck fired up on the first try, however it’s in the mid 50’s and was run 10 hrs ago.
 

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Discussion Starter #17
Fired right up after sitting overnight. Motor had to turn a couple times, but fired on the first try. I think the glow plug relay was the culprit. Thx Pat!
 
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