87 tbi 350 transplant, no spark, no voltage to fuel pump

[werewolfx13]

My 76 k20 has been on the road for a couple weeks getting a shakedown following being the recipient of an 87 tbi 350 and wiring harness, conversion from th350/np203 to sm465/np205. All has been well until it died as I lugged it a bit pulling uphill into a driveway and would not restart. Following that, diagnosis began:

Truck cranks fine. Fuel pump does NOT cycle. Checked for voltage at the pump, no voltage for priming or while cranking. Jumped the test lead at the fuel pump relay directly to the battery, fuel pump runs, and fuel pumps to the throttle body with good pressure. Truck will NOT start. Checked for voltage at the coil, solid 12v. Replaced ignition module and pickup coil, truck still will NOT start. Fuel pump will NOT run without being jumped to the battery.

I do not have a CEL hooked up (76 cluster minus its printed circuit, all aftermarket gauges except speedometer), will be buying a basic obd1 reader and fuel pump relay, and will confirm no spark.

New parts already installed either now or during the light refresh of the motor:
AC Delco Cap & Rotor
BWD Ignition Module (replaced at the refresh, and again today in spite of the first one testing good)
BWD Pickup Coil (original AC pickup was out of spec for resistance, and the plastic connector that plugged into the module was missing)
Plug wires
AC cr43ts plugs
Precision Fuel Pump
Wix spin on fuel filter setup

Fusible links @ firewall have solid continuity and voltage across.

Fusible link @ starter replaced with a weather sealed automatic reset circuit breaker, already disconnected the battery for a minute and reconnected to rule it out, but continuity is solid all the way across anyway.

Afraid of it being bad ecm?

Thanks in advance, I will be working at least the next 7 days and trying to recover from a cold, and wont have time to perform any more tests until then.

[bd]

Check the ECM B and ECM I fuses.  Use a test light to check for battery voltage on both ECM B fuse box socket contacts then check for ignition power on both ECM I fuse box socket contacts.  Probe the contacts, not the fuses.

[werewolfx13]

Will do, fuses were good but didnt probe the contacts

[bd]

Is the fuel pump OPS located adjacent to the distributor installed and connected?  Does the orange wire at the fuel pump relay measure B+?

[VileZambonie]

Did you also check the ECM grounds and connections at the ECM?

[bd]

Just as a sidebar, poor ECM connections were such a common problem on the LD and MD trucks in the 80s and 90s that any unusual driveability complaints routinely precipitated cleaning and retensioning the terminals in the ECM board edge connectors.  ECMs can fail, but it's uncommon - they are pretty durable considering their operating environments.  Connections on the other hand can cause plaguing symptoms that come and go.  And, because of ECM internal circuit complexity, ground problems can result in all manner of irrationality. lol

[werewolfx13]

Oil pressure switch had been deleted in the donor truck, i removed the crushed connector and bundled the wires into the harness, since the ops was allegedly only a failsafe if the relay failed. The ecm connections seemed tight, but the body of the ecm is isolated in a plastic hanger. Are there supposed to be more than just the two large connector bundles that plug in to the ecm? It was quite some time ago i pulled all of this out of the donor truck

[bd]

...i removed the crushed connector and bundled the wires into the harness, since the ops was allegedly only a failsafe if the relay failed....

Perhaps this will provide motivation to reinstall the OPS.

There are only two ECM connectors, generally blue and black.  The ECM grounds through its wiring harness.  The exo-chassis doubles as an EMI shield and armor.

[Irish_Alley]

so did you ever replace the relay? the ops is a failsafe but you needed a failsafe by the sounds of it

[werewolfx13]

I have not, tomorrow will be the first day that I will (hopefully) have time to run over to where its parked and start doing some diagnosing. I'll pick up a new relay and an obd 1 reader from work, my noid light set from my shop, and hopefully a bit more patience, and maybe a weeee bit of luck.

[werewolfx13]

.....Installed new fuel pump relay, still no joy. Connected a noid light and had somone else crank the engine...no light lit at all. Checked for voltage at ecm fuses...good voltage on both..decided to re-check the fuses and put some strain on them, first one was fine, second one tested fine, and then I tried to tweak the fuse....no more continuity, let off of it, continuity returned....installed new fuse...truck started...DOH .....dialed in the timing again and it drives fine again. I do feel better about having a new pickup coil, and now having a spare FP relay in my spare parts box.

Thanks for all the advice.

Noticed a new potential issue though: One injector pod gets fuel pooling around the electrical connection when you cycle the fuel pump a few times. When running, if you crack the throttle, both injectors spray a nice fine mist of fuel like they are supposed to. Thoughts?

[bd]

Replace the injectors and o-rings.

[werewolfx13]

Was afraid of that, thanks.

[Irish_Alley]

curious did you ever fix the issue?

[Hammerhandle]

For Future Reference for Anyone converting to a TBI Donor, this took me pouring over the electrical diagram for about 1 hr to find my issue, and 15 mins of probing terminals looking for power / verifying ECM grounds with the Fluke after making connection.

I had the same symptoms, no fuel pump prime, and no injector signal **also no check engine light which was a give away ECM did not have power** (this may not have been the same issue since OP didnt report his solution)

I assumed I had all connections made, because i had taken detailed photos from donor. Well one wire was missing from donor, the power wire from the battery to the Alternator thats shown in the wiring diagram, Im not sure why or how it was missing from the donor, but i did not verify operation before transplant (small mistake IMO)
This wire feeds power to ECM (and others like fuel pump relay)

If this helps anyone save some hair pulling, or grey hairs, im glad I could share.