Help me diagnose last couple bugs on the swap.

[dartslantsix]

I need some help diagnosing the last couple issues on my magnum swap. First, let me list my setup: 1994 5.2L out of a Grand Cherokee, factory pump mounted in the tank, fuel regulator is the factory style on the rail, PCM is from a 94 manual trans Ram, using an AX15 transmission. Intake plenum is fixed. Everything is basically stock.
New stuff: plugs, wires, cap, rotor, IAT sensor, Coolant temp sensor, Idle air valve, MAP sensor, O2 sensor.
EVAP is removed as well as EGR. Injectors and rail were cleaned. Cam sensor has been sync'd.
Codes from the PCM are for AC fault, EVAP and EGR.

I have two issues with the performance:
Cold start seems to crank longer than typical before it fires. If I shut off and restart within 5 minutes, it starts as normal. After an hour, it cranks long again.
Second problem is during acceleration, the motor hits a certain rpm and feels like it loses power. I don't have a tach so I don't know what rpm.

I think it could be one of three things: Not enough fuel, weak coil or PCM issues.

Here is what I've tested so far:
Coil resistance readings are out of spec, but it still gives a bright spark.
Fuel pressure is 32 psi at idle, the FSM says that is correct. At idle, I pulled the vacuum line from the regulator and the pressure went up to about 39 psi, which is in spec. I tried reving the engine and the pressure went up slightly. When I shut the key off, pressure drops to about 2 psi within a couple minutes. I have not tried a capacity test yet, so it is possible the engine is starved for fuel at higher rpms.

What should I test next?

 

[67Dart273]

I think first thing I'd do is rig a pressure gauge and monitor fuel pressure. Second is change the coil. Some of the guys on here know I dislike "throwing parts" (and money) at a problem, but you said the resistance is out of spec. That, and the symptoms, would be enough to convince me.

"Wrenches" in the gears.........

What year/ make model is the car body?

What are you doing for fuel tank venting?

Other things I'd do, even if you have to "rig" something, is monitor voltage to the ECU and whatever supplies the coil on startup, and get a spark tester and confirm that you are actually getting a good hot spark during start.

If you cannot do anything else, make certain the coil is getting full voltage in crank.

Make sure the ECU grounding is properly done. (And for that matter all of it.) Is the battery grounded direct to the block, or rear mount, or what?

 

[340dartley]

Hook up the fuel pressure Guage and go for a road test. Fuel pressure should remain steady even under heavy throttle acceleration. If you see pressure drop when you are standing on it then you have fuel supply problem. If you can hook a scan tool up to it then watch your adaptive memory short and long term. If it is trending way positive then you have a fuel supply problem.

 

[jos51700]

To me, those both scream fuel pump. Bad anti drain back and possible dirty sock or filter.

 

[magnummopar]

Your system should hold pressure for at least 1/2 hr or more. Bad regulator, leaking injectors or leaking fuel line/system. Fix this prior to looking any farther!

 

[dartslantsix]

I tested all the injectors and cleaned them out, so I believe they are good.

I'm assuming there is some sort of check valve on the supply side? Google is saying there may be one in the pump?
The regulator would also have to seal, correct?
How do I test which of these items is bad?

Edit:
Just read the FSM, which has a great explanation of the system. There is a ball check valve on the outlet of the pump. The pressure regulator is supposed to seal the return side.

Tomorrow I'm going to pinch the hose to see which side is leaking. My hunch is that it is the pump. Will update later.

 

[dartslantsix]

I tested all the injectors and cleaned them out, so I believe they are good.

I'm assuming there is some sort of check valve on the supply side? Google is saying there may be one in the pump?
The regulator would also have to seal, correct?
How do I test which of these items is bad?

Edit:
Just read the FSM, which has a great explanation of the system. There is a ball check valve on the outlet of the pump. The pressure regulator is supposed to seal the return side.

Tomorrow I'm going to pinch the hose to see which side is leaking. My hunch is that it is the pump. Will update later.

Okay, so I just got back from a long drive and the car seems very happy now.

I kind of shotgunned it, but not without merit. I replaced the pump, regulator and the coil.
Before doing all this, I clamped the return side and noted that the pressure dropped slower than when it was unclamped. I could not clamp the supply side because it is braided PTFE hose. So, I figured both regulator and pump were leaking.
I replaced the coil because it was out of spec and not very expensive. Anyway, car is running much smoother now and starts much better.
Thanks for everyone's help!

 

[AJ/FormS]

I'd just like to say that on the early systems I think the computer checks for the cam-sync signal every time the engine is cranked. This means that if the engine stopped just after the sensor, she might have to crank at least 2 revolutions before the sensor signals. If it misses that one, it will have to go 2 more.and so on.Sensors get tired.......

 

[magnummopar]

I'd just like to say that on the early systems I think the computer checks for the cam-sync signal every time the engine is cranked. This means that if the engine stopped just after the sensor, she might have to crank at least 2 revolutions before the sensor signals. If it misses that one, it will have to go 2 more.and so on.Sensors get tired.......

The pcm looks for CRANK sensor not cam and the cam sensor sends a signal each rotation of distributor to pcm for injector timing only.

 

[AJ/FormS]

That works on batch injection, but
On sequential, the pcm needs to know that the #1 is on compression. The only way to know if #1 is on compression, is from the cam signal.
Am I wrong?
Or are 94s using the missing tooth crank trigger.