Battery shorted out on hood and burnt out ECU and wiring harness. All has been replaced and everything works except no fire to fuel pump. Engine runs when jumper wire puts fire to pump. Any ideas? Thanks, Don

No fuel pump and no ignition. That sounds like the immobiliser does not recognise the ECU or engine management system.
Good luck with that then!

If your Mercedes C200 W202 is not firing on two cylinders, and you've already changed the coil packs, plugs, fuel pump, and filter, here are a few other things you can check:

1. Check the fuel injectors: It's possible that the fuel injectors on cylinders 2 and 3 are clogged or not functioning properly. You can check this by swapping the injectors with ones from another cylinder and seeing if the problem moves with the injectors.
2. Check the wiring harness: The wiring harness that connects the fuel injectors to the engine control unit (ECU) may be damaged or have a loose connection. Check the wiring harness for any signs of damage or corrosion, and ensure that all connections are tight.
3. Check the ECU: The engine control unit (ECU) may be malfunctioning and causing the issue. A diagnostic scan tool can be used to check for any error codes related to the ECU.
4. Check the compression: Low compression in cylinders 2 and 3 can cause issues with firing. A compression test can be performed to check the compression levels in all cylinders.

If you're still experiencing issues after checking these items, it's best to have a professional mechanic diagnose and fix the issue. They will have the knowledge and equipment necessary to properly diagnose and repair the problem.

did not check all fuses first, every one? for sure doing #1 wrong.

EFI
rules,
1a: do not do what you did with battery NEG lug connected. ever.!
2: EFI ,all in the world CUT fuel dead 1 or 2 ways if the ECU detects spark bad, ending as seen on TV crash and burn (FUEL *****)
sure perplexed ,as we all are on 1988 super old EFI crude as heck engine EFI, learn to do the blink codes on CEL?

more, if the pump runs for 1 second each key on as many do.
Called prime pulse) that means the PCM/ECU is not happy
fuses blown !!!!!
ECU cuts fuel for this list.
1: fuses blown
2: cmp or CKP dead. (ensors)
3; spark read back or tacho dead cranking, cuts FUEL DEAD !
ICM dead? is what makes tacho wire dead.
4: TPS wired bad such that , POT wiper pin is 3 to 5 volts DC.
this means wot mode or TPS throttle angle near 100% this activates
ECU's cut fuel mode , AKA,, unflood the engine cranking and cuts fuel
5; a bad PCM , working on EFI with BATTERY NEG and POS connected.
old ECU do not like any kinds shorts, you make messing with EFI parts
thus rule #1a , do not blow up ECUs is the rule.

I have bench tested, 88-95 ECU's
and learn all this, by using home made tachometer generators
and tested all inputs to learn that, what works and what does not work;. (and why)
when cranking some sensors are not used at all
or goes to limphome but does run. using crude limphom rules

for sure one input tot he ECU is dead wrong
well hope, that and not bad ECU./

You say (it all began when), please explain what happen > you were driving along and all of a sudden ......your turn !!!. i have a couple questions >> You do realize that the key has to be turned to the "on" position to excite fuse block wiring and unless you had a wiring harness short and cooked the wiring or have disconnected wiring , common sense says it's not the wiring, as for the fuse box & block , simply google "1997 chevy tahoe/wire harness & you can probably find info. on (you tube) searching the same way !!

YOU HAVE FAULTY FUEL LEVEL SENDING UNIT ON FUEL PUMP ASSEMBLY OR LOOSE GROUND WIRE TO FUEL LEVEL SENDING UNIT CHECK WIRING HARNESS GOING INTO FUEL TANK.COULD HAVE SHORT BROKN WIRE IN WIRE HARNESS TO PUMP ASSEMBLY.

FUEL PUMP MORE LIKELY WORN OUT SHORT OUT.BESURE REPLACE FUEL PUMP WIRES IF FUEL PUMP HAS TO BE REPLACED.CODE SCAN FOR ECU FAULT. IF FUEL FILTER STOPPED UP FUEL PUMP WILL SHORT OUT.

The first thing you should do is to locate the oil pressure switch/sending unit.

This switch serves two functions.

1) provide oil pressure reading

2) disable the fuel pump relay in event of oil pressure loss.

===

When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.

ECM1 fuse blow is because the harness is grounding/shorting.

===

DO NOT drive the truck until you change the oil pressure switch.

After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.


Please post up day on the comment window/page.

I will follow up on it later.


Good luck.

Check your o2 sensor harness. The harness if not properly secured will rub on the axle to a point where it rubs through the insulation of the wire & shorts on the axle causing the ECU fuse (20A) to blow. Repair the harness & replace the fuse & bada bing! You should be in business! Hope that works. IF NOT follow this K.I.S.S.

Keep It Super Simple! It never fails!

there is no such thing as a main battery fuse.
seems like a wire has come undone under the dash and shorted your car out.

check the fuse box under the hood and make sure the fuel pump fuse is not blown.
if the fuse is blown, replace it and see if you have any fuel/spark. the fuel pump fuse controls almost everything electrical under the hood. if the fuse keeps blowing, then there is a short sumwhere in the engine wiring harness.