88 2.9L No Fuel pressure, only 7.5V through the inertia switch

[BillRod]

HI All

88 Ranger, 2.9L V6, 5speed, 4x4, ext cab,
No power accessories, no air, no cruise.

External fuel pressure gauge shows NO pressure at all on the fuel rail.
Using Tpins I probed the wires on the inertia switch and there's only 7.5V going through the switch.

Is 7.5V normal?
My Chiltons of course does not show that detail so I'm not sure if that's a symptom to add to the mix or if 7.5V is normal.


We went 4 wheeling over the weekend and after 3-4 hours of rough trails and steep inclines the engine just stopped as if it ran out of gas.
Tank is 3/4 full.

My first thought is being 20 years old and this is it's first time out on rough bumpy steep trails we mixed up all the dirt and crap in the tank and either clogged up the new filter (about 1000 miles old is all) or we killed one of the fuel pumps.


Went back the next day to tow it home and the battery would not turn over the truck. Had the truck 6 or 8 months and this is the first time the battery ever had an issue. I put a charger on it and I am charging the battery.
The 7.5V is with the charged battery and the charger still on the battery.

Turning the key I hear a relay click somewhere near the airfilter box.
But I do not hear the front fuel pump, I don't think I have ever noticed any sound coming from the front pump but I have never listened for that either.

Symptoms so far.
1) Lots of rough and steep trails bounced the truck around a lot.
2) No fuel pressure.
3) Battery suddenly or coincidentally lost or loosing charge.
4) 7.5V going in and out of the inertia switch.
5) No sounds from the front fuel pump.
6) clicking sounds from the near the airbox.
No flashing engine lights or anything.


I have not done any other diag's yet, Hope to get to that this weekend.
I do have a obd1 that I will use as part of the diag's.

Any thoughts before I start taking stuff apart and diagnosing it?

Thanks
Bill

[Area 52]

Why do you only have 7.5 volts?
Start at your power source...battery....bat cables...etc.
For this to abruptly happen, I would think you have a bad battery connection (slow cranking). Remote possibility your battery is shot. What is the fully charged voltage on the battery?...should be 12.7 give or take a half volt (charger disconnected).

[351rangerxxx]

you using both volt meter leads on the wires at the same time or is one at ground and then checking each wire on its own?

[351rangerxxx]

bye the way i got the tank mounted pump if theres one in the tank and i might still got the frame mounted one also. i probably got a safety switch to if you would like cheap good used part to test with. 15 dollars for each one shipped. 6 for the switch

[Earl43P]

You are probably using a convenient spot on the chassis near the inertia switch as your ground. It is likely that your chassis ground is compromised / gone, resulting in your problem. Start at the battery - terminal and verify your grounds there. Move on to block to windshield wiper motor bolt ground strap, then underneath about midway, you should find a frame to chassis ground strap. Somehow during your off roading, you may have worked a ground loose; that's where I'd start. If I recall correctly, the fuel pump ground is on the DS fender under the hood, unlikely to be compromised. The ones directly to the battery, radiator support and under the truck seem like a good place to start looking/cleaning/verifying.

Using the ohms scale, touch the leads together and note the continuity reading. Then start touching one lead from Bat- to rad support, fender, frame, block, etc. You'll be looking for the same or very close to the same continuity reading as when you touched the leads together.

I've also heard that some older models used a ground at one of the starter mount bolts. Take a look for that one while you are underneath.

If your meter skills are lacking, you can take a jumper cable, attach one black clamp to the battery- and the other black clamp to all those places I mentioned above. You'll need bright metal to make sure that works, but try to crank it / hear FP with that "new ground" in various places. Crude, but effective.

If none of that works for you, go after the battery + side.

[BillRod]

Originally Posted by 351rangerxxx

you using both volt meter leads on the wires at the same time or is one at ground and then checking each wire on its own?

Voltmeter with one on the chassis metal for ground and the other probing the wire.

Battery at 12.5 volts, but did not have enough power to crank so I added my charger so the battery may well be bad.
However I did have the charger on the battery when I probed the wires so I should have had full voltage at the inertia switch.

I will check this weekend for wire connections and stuff.

Bill

[Area 52]

Originally Posted by BillRod

Voltmeter with one on the chassis metal for ground and the other probing the wire.

Battery at 12.5 volts, but did not have enough power to crank so I added my charger so the battery may well be bad.
However I did have the charger on the battery when I probed the wires so I should have had full voltage at the inertia switch.

I will check this weekend for wire connections and stuff.

Bill

Bill...totally disconnect the ground cable from the battery to the chassis...what shape is it in? Look under the insulation on both ends too. File/wire brush the chassis and cable end...put it back on if cable appears to be good. Tighten the hell out of the chassis bolt and then spray paint over it to inhibit future corrosion.

[rpstevens]

My 1988 Bronco II had a similar problem, I found that one of the ground wires came loose and then the safety switch went out. After I replaced those, my pressure was still down and I had to rebuild the pump inthe tank.

[BillRod]

I cleaned the ground on the batt.
Used an ohm meter from the terminal to the engine, frame, body, a bunch of places and it's all just about zero ohms.

With a volt meter on the intertia switch wires, when I turn the ignition switch on it reads 12.5 for a second or so then it drops to 9 or 8.
Battery reads a consistent 12.5.

Same thing when I measure it under the hood at the inertia switch connector is near the air box.

[IMenriched]

there is ground near the ecm, (passenger side ,just in front of the door), remove panel. double check there for voltages.

is the voltage drop before or after the inertia switch??

might want to load test the battery just to make sure a plate/cell isn't broke loose inside of it. if you haven't done so already.

[Earl43P]

Replace the fuel pump relay and PCM relay.

At the very leaast remove the FP relay and check the voltage there. Could even rule it out with a jumper across the sockets. I went to consult here on which pins to jump (not relying on memory for much anymore)

http://dlcparts.com/images/BoschGuide.pd

then figured, let YOU download it and learn something new today. Most relays have a pin schematic on one side too.

Might look here too, shows how the PCM relay pulls in and gives power to the FP relay. http://www.therangerstation.com/tech...ls2_9_1of3.JPG

[BillRod]

With new ones being $50 I went down to the Upull and Pay and for both relays by the air box.

Swapped them each in but no difference at all.
What are the odds of 2 having the exact same issue?

The link to the diagram works.
I printed that out and will compare that now.

The http://dlcparts.com/images/BoschGuide.pd link does not.
Am I doing something wrong with that?

Thanks Bill