Please help, folks...!

My typically reliable 1988 F150 "farm truck" (XLT Lariat, straight 6, 300 CID, 5 speed manual, standard cab, longbed, dual tanks, 34,357.9 on odometer that has flipped over three or four times--not sure which, 2nd alternator, 2nd OEM transmission, replaced water pump twice but no major engine work...) suddenly quit starting. Rear tank is completely full. Front tank is half full. Engine will not fire with tank selection switch in either position. Engine has spark (...however, I only tested the three front plugs).

Years ago on a long drive (late '90s??? I forget exactly when Lol) the same thing happened and some Ford dealer in the middle of Illinois ended up having to replace the fuel pumps in both tanks.

I have an Innova 3145 Ford OBD1 code reader (EEC IV - MCU), so since "O' Henry" won't start all I can get are KOEO (Key On Engine Off) and CM (Continuous Memory) but no KOER (Key On Engine Running) codes.

Two codes* are reported:
87-O ("Primary fuel pump failure") and
96-C ("Fuel pump secondary circuit fault / high speed fuel pump relay open").

Am I correct that this truck has three fuel pumps, that is, one in each tank and also an external "main" or "high pressure" pump?? What is the next test or part replacement I should do?

_______________
*O, R and C Icons: These icons indicate the type of test being performed and indicate if the code being received
is a KOEO, KOER or CM code:

• O = Key On Engine OFF (KOEO) Test/code
• R = Key On Engine Running (KOER) Test/code
• C = Continuous Memory (CM) code

 

If you squirt fuel in the Throttle Body, does she start ?

You should check your Fuel Pressure at the Fuel Rail.

If the Fuel Pump Relay is original, I suggest you replace the well-known substandard Relay Ford was using until the 90s.

Check the wiring in the Fuel Pump Relay Socket.

If you jump pins 2 & 6 on your Self-Test connector do you hear your High Pressure Fuel Pump running ? If not, check your Inertia Switch.

 

Is green the fuel pump relay socket or the computer relay socket?

These are the old relays beside the boxes of the new relays purchased from O'Reilly's.
Thanks, vjsimone. Turns out it was the fuel pump relay.

I had first suspected it might be that OR the computer relay and had bought replacements of both from O'Reilly's, the only "local" (60 mi. round trip drive Lol) parts place that had them in stock. Unfortunately when I put them in, it wouldn't fire and started returning the codes in my original post.

After reading your reply, I thought maybe I put them in the wrong relay sockets? Swapped them and still no start and figured well, time to try all the more difficult tests you suggested. 😞

But first I decided to double check what relays they sold me (See photos. Note these are the old relays beside the new relays' boxes. Not sure but I think the OEM Ford green-colored relay AND the green-colored relay socket are the fuel pump circuit's??) and noticed their site said one of the two they sold me "doesn't fit your 1988 F150!" So I replaced it with the non-green old relay, and "O' Henry" fired right up!!!!! 😀😁

Now, maybe we can figure out why it "idles" at 2,000 RPM! 😮 But I will create a new post for that. 😉

 

You will want to check all of your vacuum lines and probably replace them one at a time to check for the high idle initially.

 

The green one is the FP Relay.

 

Thanks, that's what I suspected but wasn't sure.

I'll need to make a trip to a parts store for a supply of vacuum hose, but in the meantime it's throwing a couple codes. Here's the new thread:

• https://www.ford-trucks.com/forums/s...6&goto=newpost