3900 V6 Swap help me get it running.

[Guest]

Using A1 code for 91 Beretta 3.1 L.

30 lb/hr injectors installed in place of stock 27 lb/hr

Engine started twice and ran for about 4-5 seconds, afterwards it attempts to run but can't quite catch.

I'm getting 3 confirmed codes as they reappeared after the battery was disconnected for several minutes and reconnected, one I expect.

15 CTS low, I confirmed 5 volts are present at the plug. Used a loose
sensor if it has to be grounded that may be the problem.

34 MAP low, confirmed 5 volts at plug

54 FP volts low, shouldn't be a problem, I didn't connect the sensor wire. Pump works fine.

In order to get the engine to run I had to press the accelerator to the floor and hold it to get the best results but it didn't seem to respond to well to pedal application while it ran.

TunerPro:

CTS reads -38.65
water temp shows 104 deg, problem is there is no water in the engine yet, and there is no water temp sensor I'm aware of, only the CTS and IAT sensors, it's no where near 104 degrees outside.

[CNCguy]

Joseph... Are terminals "A" on the CTS & MAP grounded to the engine or do they do they connect to terminal "BB6" on the ECM? Or if the wire going back to the ECM has a bad connection it would make both sensors not work correctly as the MAP would be feeding voltage to the ground side of the CTS.

Good to hear you are back at making progress.

[Joseph Upson]

Joseph... Are terminals "A" on the CTS & MAP grounded to the engine or do they do they connect to terminal "BB6" on the ECM? Or if the wire going back to the ECM has a bad connection it would make both sensors not work correctly as the MAP would be feeding voltage to the ground side of the CTS.

Good to hear you are back at making progress.

I back probed the harness a while back but I'm going to check it again tomorrow. Both sensor grounds go directly to the ECM and the MAP reading changes as the engine is being cranked. I don't know the history on the map sensor so it's possible it could be bad.

I'm going to make a change to the 8F code tomorrow because that's what I plan to run. I switched the injector flow rate from 16 lb/hr to 30 lb/hr that should lower the amount of fuel being injected on startup when the computer corrects for it in the A1 code. I'll also need to put the timing light on it and see where I am relative to the TDC marks I put on the balancer and timing cover.

[Superdave]

are you using an emulator?

the injector flow rate is just a display in the $A1.. iirc it dosen't do anything. you need to lower the bpc constant to get the fueling in order.

[Joseph Upson]

are you using an emulator?

the injector flow rate is just a display in the $A1.. iirc it dosen't do anything. you need to lower the bpc constant to get the fueling in order.

Yes, and I'll do that instead.

[Joseph Upson]

Finally got it to run however, there appears to be two cylinders missing so it's not smooth. I haven't tried the TGP code yet but I believe it will be much closer in tune since it uses ~23 lb/hr injectors instead of the 16 lb/hr injectors the A1 engine uses. When I performed a litre/inj ratio for the TGP 3.1 using 24 lb/hr rating and then applied it to the 3900 the result yielded a requirement of 30 lb/hr injectors (which I have) for the displacement increase to properly fuel the 3900 with the same injector reserve.

Now I have find the cause of the skip, hope it's nothing complicated.

[CNCguy]

Did you find which cylinders are not firing? Both cylinders on the same coil? I always used a quick touch to the exhaust manifolds to check which cylinder was missing but after the last blisters decided to buy a cheap infrared thermometer from Harbor Freight for $40. Very handy to have around and much easier on the finger tips.

[Joseph Upson]

Did you find which cylinders are not firing? Both cylinders on the same coil? I always used a quick touch to the exhaust manifolds to check which cylinder was missing but after the last blisters decided to buy a cheap infrared thermometer from Harbor Freight for $40. Very handy to have around and much easier on the finger tips.

I put a different set of coils in so I'll be testing it again before long. I'm working on completing the exhaust at the moment and installing all of the parts so I can focus on tuning. If the coil change doesn't fix it that leaves the ignition module and the injectors. I'm really hoping the coil pack takes care of it because I certainly don't want to have to bother the injectors but if I can isolate the non firing cylinder that would help narrow down the problem.

If the engine fires on all cylinders with a blast of ether while the engine is running I'll know it's an injector problem.

If I confirm spark at all cylinders again it could be an injector problem. If not an injector next the wires because I took the stock plug wires and fitted them with the ends from another set of wires to convert them to fit the earlier coil terminal studs.


I'm hoping because if that doesn't fix it I'm scared. The sound of the turbos spooling up sure sounded nice.