'94 Cranks, won't start. No CEL.

[AronAZ]

Was driving and the engine quit. No warning. All other power stayed on.

Engine cranks but won't fire up. There is no CEL when the ignition is switched ON.

All other accessories worked: radio, horn, headlights, turn signals, emergency flashers.

I replaced the fusible links at the battery.
I replaced the 90987-02004 EFI relay under the hood.
I replaced both 90987-02004 relays at driver's kick plate (couldn't tell which was for EFI so did both).
Checked 15A EFI fuse under hood and fuses on dash - all good.
Checked the connection at the fuel pump relay (but have not tried to jumper yet).

Result is the same. Read through a bunch of threads & helpers. Ideas?

TIA

 

[Tools R Us]

Do you have battery voltage at the B+ term in the diagnostic plug?

 

[AronAZ]

I'm going to grab a volt meter in the morning and check. Thanks.

 

[AronAZ]

I have +12 at the fuse box screw head, +12 at 15A EFI fuse, +12 at the EFI relay pin 2 (lower left if standing driver's side fender), but nothing at pin 3 at the EFI relay or (pin 12?) B+/E1 diagnostic port.

If it matters, I get +12 at the ECU-IG & ECU-B fuses in the dash.

Which of the 2 relays is the EFI at the driver's kick plate? If no power at pin 3 EFI relay when ignition is ON or at diag B+, where would be the break point be?

Thanks again

 

[Tools R Us]

With the EFI relay plugged in, when the key is cycled to run does the relay click?

Pin 3 at the EFI relay should show voltage with the key on. Pin 1 is ground. Pin 4 should have continuity to B+ in the diagnostic plug, if not, unplug the connector between the distributor and P/S fluid reservoir, the yellow/red wire should have continuity to the B+ in the diagnostic plug on the engine side and to EFI relay pin 4 on the fenderwell side.

 

[AronAZ]

I hear something clicking but can't validate its the EFI relay for sure.

Pin 1 at the EFI relay has continuity to ground. Pin 3 still has no power with ignition ON. The connector you mention has no power with the relay installed & ignition ON. But if I jumper EFI relay 2-4 it gets power. So I'm guessing the issue is between EFI relay Pin 3 & the ECU?

 

[LandCruisinMy93]

Are your injectors firing when the key is turned to the on position? Can you smell fuel when you remove spark plugs? Have you checked for spark by pulling a wire and inserting a good plug into the boot and grounding the threaded portion? If you have spark and fuel it might be a timing issue, whether it is a timing issue mechanically or electrical issue is a different story. If you have spark and no fuel test your mass airflow sensor curcuit. If that checks out then check the cam positikning sensor circuit. Let us know if anything works

 

[Reelitchy]

Tools mentioned the connector at the distributor. Check that. You should have 12 v on both the red wire and the yellow/red wire. That connector feeds both sides of the relay. The yellow red is from the ECU and powers the relay-pin 3

 

[AronAZ]

OK, let me correct & amend my earlier post based on your additional input and looking closer at both the low side & high side of the connector.

At the connector (low side, male from what looks like the main harness to the fuse box and looking directly at the connector), with the relay installed there is +12 at the top right pin only. If I jumper the relay pin 2-4 I also get +12 on the bottom right. With the jumper in place I also get +12 at the B+ in the diagnostic port (when the connector is connected). I tried 2 new relays, both have the same result - I'm guessing because there is 0v at pin 3.

On the high side of the connector (female, going towards the intake) there is no power. I see 0.01v on the bottom right which I think would correspond to the +12 coming from the top right of the low side (like the .01 is "detection" level power maybe).

Thanks again for the help. Much appreciated.

 

[Dragos80]

Maybe this thread helps:
https://forum.ih8mud.com/threads/em...-item-recommend-keeping-copy-in-truck.115816/

 

[Reelitchy]

At this connector you should have 12 volts on pin 3 and 4 going up through the manifold ( key on).I suspect you don't have 12 on pin 4. You Will probably have to chase that wire along the harness. Since you jumpered 2 and 4 on the relay block that bypasses the relay- have you tried to start the truck with it jumpered?

 

[Tools R Us]

I hear something clicking but can't validate its the EFI relay for sure.

Pin 1 at the EFI relay has continuity to ground. Pin 3 still has no power with ignition ON. The connector you mention has no power with the relay installed & ignition ON. But if I jumper EFI relay 2-4 it gets power. So I'm guessing the issue is between EFI relay Pin 3 & the ECU?

That would be my guess. Pin 3 (the red wire) turns the relay on. Check it at the ECU, if there is key on power there, the problem in the harness. If not, it's likely an input to the ECU, check all of the key on inputs per the EWD. Most likely suspect would be the black with blue stripe from the IGN fuse to the D connector pin 13.

 

[ton504]

Usually a fuel prob wont trigger a cel. Squirt some throttle cleaner or something flameable and turn it over. Or put a gauge on the fuel line.

 

[AronAZ]

View attachment 1032154View attachment 1032155
At this connector you should have 12 volts on pin 3 and 4 going up through the manifold ( key on).I suspect you don't have 12 on pin 4. You Will probably have to chase that wire along the harness. Since you jumpered 2 and 4 on the relay block that bypasses the relay- have you tried to start the truck with it jumpered?

On the male end (left image on the diagram) there is always +12 on Pin 3. Pin 1 only lights up +12 when I jumper the relay. Pin 4 never has power.

Does not start with with EFI jumped, I'm guessing because the CEL/MIL never turns on during the self self check when the ignition is switched ON so the ECU doesn't signal the rest of the system. Googling for diagrams to see what that pin 4 is fed from in that connector.

 

[Reelitchy]

Pin 4 comes from pin mrel on the ecu. I don't have the diagram now but if you search the forum for "94 FSM" there is a link with the diagrams etc.
Sorry out of town - checking out the snow in va

 

[jonheld]

If this was a 3FE engine, I would tell you that with no CE light with the ignition switch in the ON position, this engine will not fire. The ECU is not initiating fuel delivery and spark. With no CEL, there is no need to even crank the starter.
If this was a 3FE engine, I would ask you to simply unplug the AFM connector and see if this has any effect on the CE light.
If this was a 3FE engine, I would ask you to reseat the TPS connector and the ISC connector. If no change, then test according to the FSM.

The ECU fires the CEL as a tally lamp before starting to let the operator know that "all systems are go".

 

[AronAZ]

Pin 4 comes from pin mrel on the ecu. I don't have the diagram now but if you search the forum for "94 FSM" there is a link with the diagrams etc.
Sorry out of town - checking out the snow in va

I found them - thanks. I'm struggling to figure out which output on the ECU should be giving +12 to feed EB1 pin 4 / EFI Relay pin 3. The diagram indicates a solid red wire from EA7 pin 3. I see 2 red wires that each have silver dashes on them. One is on the corner of the ECU connector and the other is in the middle. With the smaller of the 2 ECU connectors pulled, the one in the corner only gives +0.6v when the ignition is ON (+0 when off). The red-brown, red-white, and yellow (with silver dashes) give +12 as does the red-blue on the opposite corner.

 

[AronAZ]

Oh, and the output on the ECU was not affected by swapping the EFI relay with the 2-4 jumper.

FWIW - I also jumped the +B to FP in the diag port (with the 2-4 relay jumper in place) and the fuel pump kicked on fine.

Is there something upstream that I'm missing? A fuse/relay that could stop the ECU from signaling the EFI relay?

 

[Tools R Us]

... A fuse/relay that could stop the ECU from signaling the EFI relay?

IIRC, the key on signal comes from the IGN fuse in the interior fuse box to the ECU.

 

[AronAZ]

Sorry. Disregard Post #17. I can be a dumbass sometimes.

ECU pin 3, solid red wire = 0v with ignition ON. Same result with & without EFI relay 2-4 jumper.