Fuel Pump has called it quits I think

[shojuan]

I guess my aging fuel pump didn't take too kindly to having abnormally high amounts of gas flowing through for the duration of the Pinnacles outing. When I got home I noticed a slight
drop in power coming off the light into San Juan so I pulled the codes to see what gift the SHO had for me. 87 and 96:

87 Fuel pump circuit fault (check inertia switch) intermittent in fuel pump primary circuit

96 Fuel pump monitor circuit shows no power
AIR Bypass (AIRB) not working (Service 87 code first if present) Fuel pump relay or battery
power feed was open

When I turn the key on the fuel pump cycles for only about 50ms instead of the normal 1-2 seconds. The car does start and idle however.

If any of you guys think this could be anything but a bad fuel pump let me know soon because I'm about to spend $80 for a new fuel pump in the next few day. Should I even bother checking the associated wiring before I replace the pump? I just put in a new ICRM module on Saturday and that cured all the major issues I was having with my car. It was solid as a rock until those codes. I really don't want to have to go backprobing those circuits. (Unemployment makes me lazy, and shiftless. But mostly lazy )

 

[89 black SHO mtx]

try running a fuel pressure test on it. its simple and it will tell you if you are getting the right pressure. the short burst before start is weird. if the pressure test is fine you might want to have it volume tested and go from there. it is easier than replacing a good fuel pump and having the same problem.

 

[Yamaha V6]

FYI the $200+ fuel pump & sender unit for the 89-only (Motorcraft) is long discontinued (search archives for part number & dealers that had them). I had one of the last 7 shipped up last fall / winter from a dealer in NJ on the locator service. Of course now I'm going to end up parting the freaking 89 for body & mechanical parts for the 91 (alt, starter both new, etc.)

Best of luck Rick.

 

[MeShoHorny]

Check the fuel pressure at the rail 1st. IIRC, it should be 40psi +/- 2psi with the vacuum line from the FPR disconnected @ idle.

Does the fuel pump make a high whining sound, more louder then before?

If you find the pump is going out get a new one from Auto Performance Engineering

155lph or 190lph should do ya fine.

 

[shojuan]

At one point yes it did make a higher pitched and louder whining noise. It isn't doing it now. The latest behavior is I got in the car today and cycled the fuel pump a dozen times or so. The same 50ms short burst BS like yesterday. So I started the car up to see if it would die at some point. Nope, it ran for several minutes then I shut it off. Then I cycled the fuel pump again several times and it's back to doing the full 1-2 second pre-startup cycle.

I've been wanting to do a fuel pressure check for sometime now. Unfortunately nobody I know has a fuel pressure gauge. Nick Chrimes doesn't even have one. None of the parts stores will lend them out so I'd have to spend $40 to buy one. I guess I should, but in all honesty I'm just more inclined to take my chances spending $87 on a new fuel pump. I'll get the 190l/hr Walbro unit from Auto Performance Engineering.

Does anybody know someone with a fuel pressure gauge in my area?

 

[shojuan]

I guess I should get off my duff and run these tests that Steve so kindly took the time to type up the procedure for: http://www.shoforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=17;t=003274#000010

 

[Off Road SHO]

SHO_JUAN
Just use a cheapie tire pressure guage, you know the pencil type. If you don't want to do that, use the fill hose off of an old can of Fix-a-Flat and attach it to a cheapie dial air pressure guage. Throw it away if the gas melts it.

Tom

 

[shojuan]

Tom, I've tried that before with a tire gauge but on my 89 the valve core is too far recessed in the schraeder valve for the tire pressure gauge to reach it. I tried it again today with the cheapie tire gauges and my nice dial gauge. I also found a tire chuck I wasn't using and it looked like it could make it but it still would get down far enough onto the valve core. I'll keep a look out for a can of fix-a-flat and see if I can find one with the hose and screw on adapter that looks like it will reach the valve core. Thanks for giving me that idea.

Jay, I put the fuel pump in its test cycle (grounded fuel pump test pin). The pump runs nice and loud and then after several minutes it got very quiet where I had to get up close to hear it pumping. During the KOEO test when the fuel pump cycles and you get the initial high pitch then the low pitch, I don't get the low pitch anymore. I suspect that this is a problem with one of the two circuits that the 89 uses. According to Steve the 89 is unique in that there are two circuits that supply power to the fuel pump, not one like on the other years

NOTE: The 89 uses a circuit that provides 2 different voltages to the FP (according to the published documents I have available). At idle, power is supplied via a dropping resistor mounted at the top center of the firewall and a relay in the ICM. At higher engine speeds, the ECA energizes another relay in the ICM which bypasses the dropping resistor and applies full battery voltage to the FP. Other years do not
appear to use this feature, but the 90 and 91 ICM schematics still show the extra relays with no external resistor. It's up to you to figure it out.

Also, at some point while going back and forth between running tests and running the fuel pump by grounding the test circuit the pitch of the fuel pump did rise to a higher pitch. Then later it returned to normal. What does all of that mean?

Ironically, for the first time in about 4 months my car got a 9 on the SEFI test. Not just one time as a fluke, but repeatedly. I guess the Italian tuneup the car got over the weekend after I installed the new ICRM module really helped clean out the pipes! It got a really nice flogging.