Slow cranking engine after rebuild

[FuNkYMoNk85]

I’ve scoured all over these forums and the internet and can’t find an answer, so here goes.

Just finished the rebuild on my 2002 4.0 and got it installed and running. Engine runs great, however I’m having a cranking issue. I replaced the batter, spark plugs, and injectors. New cam sensor and OPDA as well. Before first start I set crank to TDC on #1 compression stroke based off the vibe damper, set the cam sensor in the same direction the old was without removing the pin for TDC and then used my Innova 5610 to perform the cam/crank relearn.

I’ve had guys tell me it sounds like a timing issue, but since it’s all PCM controlled I don’t know the process for that.

Could it be the starter is giving out? Far as I know it’s the original with 276k on it.

 

[Gilaguy23]

If it runs right Id say its not a timing issue. I goofed on my 91 and installed the new dist a tooth off and it ran like poo and was a bear to start. Even with it being computer controlled I dont think it can compensate for a tooth off. How are the grounds, battery connections, etc? Load test the battery lately?

 

[FuNkYMoNk85]

Took the battery connections off and cleaned them really well, checked grounds in the block and the bonding strap to the firewall. Found the block was slightly loose, tightened them but no change.

I put a meter in the battery and checked as my wife cranked it, barely dropped below 12. Bought an Optima just a couple days ago for the first start. Only thing not new was the starter. If there’s a better load test I’m all ears to try It.

Once it finally starts after a slow crank it runs and drives great, making me think it wasn’t timing as well.

 

[FuNkYMoNk85]

Swapped the starter over, still no start. Seems to crank stronger though.

Back to the drawing board of checking for spark and fuel I guess. Strange because it ran great each time it started and now nothing.

 

[macleanflood]

Got all your grounds hooked up? Engine, chassis?

Check fuel pressure to rule it out.

Compression? Could have leaky fuel injectors and your hydro locking the engine or a cylinder. Sounds unlikely.

Could try putting the key on run and jumping the big and small wires on the starter to eliminate the ASD circuit as the cause.

-Mac

 

[FuNkYMoNk85]

Hadn’t thought about compression, I’ll add that to my list. Been trying here and my google skills looking for possible scenarios. For fuel pressure, the standard gauge I can rent from Autozone would suffice?

I’m going to recheck all my grounds, even ones in the area I never touched.

The ASD was a new one to me reading through the service manual last night, so I’ll take a look at that one too as well as the fuses and relays for starting system.

It’s an odd one to me because it struggled for literally 1-2 seconds at first start, ran great but had a check engine light, turned out to be two O2 sensor codes (I forgot to hook one up after being back/forth with my fuel rail leaking) and the IAC module. However once I hooked up the O2 I never got another code. Got through the 20 minute run at 1800-2k rpm and it ran great, struggled in the same manner but gradually worsened but ran great once started and drove well each time (have maybe 20 miles on it now) . Had my starter tested at AZ and was good, replaced it anyway just to see if the load of the engine caused an issue. Now it cranks but won’t fire…

Hopefully I didn’t wipe out my cam.

 

[macleanflood]

How long did it take to do the engine swap?

Any tester will do. Especially if they're working and semi accurate. =)

I ask because modern gas is crap...if it sat there for a couple of months it could easily have destroyed the fuel pump.

-Mac

 

[JMT]

Test the fuel pump by turning the key on for 3 sec, then off, then back on for 3 sec. Do this five times. Then turn it over and see if it starts right up. If it does it’s your fuel pump sending unit.

 

[Steel City 06]

Is your oil pump losing it's prime? That will cause the engine to run like crap for a few seconds before it finally sucks up liquid. May not throw a CEL unless there is at least 10-15 seconds without oil pressure.

 

[FuNkYMoNk85]

It sat for a little over a year with an almost empty tank, gas light came on during my 20 minute break in. Once it was up and running I drove it to the gas station and put about a half tank in it just for some fresh gas.

I’ll give the on/off a few times a try, any other way with a meter to check the pump before dropping the tank?

I don’t think the oil pump is losing its prime, had good pressure each time it was driven. Any ideas on how to check that?

My ASD/Starter/Pump relays all checked out this morning based on what I found in the service manual with my meter.

Heading to AZ now for a fuel pressure gauge and a test light since I can’t seem to find mine around here.

 

[JKP]

Pick up the fuel pressure test gauge while you're there. There's a schrader valve on the fuel rail to check fuel pressure.

 

[macleanflood]

It sat for a little over a year with an almost empty tank, gas light came on during my 20 minute break in. Once it was up and running I drove it to the gas station and put about a half tank in it just for some fresh gas.

Yeah...test it but I'm pretty confident in a bad pump.

Can't find the reference but someone posted that fuel pumps fail on full tanks...they get hot on empty because there's no gas to cool the pump...then the shock from a full tank of cold gas damages the magnet in the motor and blano, dead.

-Mac

 

[AzJeff]

Can't find the reference but someone posted that fuel pumps fail on full tanks...they get hot on empty because there's no gas to cool the pump...then the shock from a full tank of cold gas damages the magnet in the motor and blano, dead.

-Mac

Seems like every fuel pump would fail every summer in Arizona if this is legit....?

 

[macleanflood]

Seems like every fuel pump would fail every summer in Arizona if this is legit....?

Only the ones that sat for a year...

And I guess the theory is shocking a healthy pump isn't an issue. It's shocking the pump that's on it's way out... according to the postulated theory that's what finishes them off.

-Mac

 

[FuNkYMoNk85]

Hooked up gauge to the fuel rail, pump initially primed to about 22 psi. Service manual says at idle it should be 42 psi. It should prime to the same correct?

 

[macleanflood]

Hooked up gauge to the fuel rail, pump initially primed to about 22 psi. Service manual says at idle it should be 42 psi. It should prime to the same correct?

Yeah should be around 48-50.

Mine would run fine-ish around 30-32 psi but my gas mileage dropped.

-Mac

 

[FuNkYMoNk85]

Ok. I also tried to prime it by turning the key off and on a few times. It wanted to start for a split second and then back to just cranking.

What’s the trick to putting fuel in the throttle body to try that? Just pour a little to fill it with the throttle closed?

 

[macleanflood]

Ok. I also tried to prime it by turning the key off and on a few times. It wanted to start for a split second and then back to just cranking.

What’s the trick to putting fuel in the throttle body to try that? Just pour a little to fill it with the throttle closed?

Brake cleaner or starting fluid.

-Mac

 

[JMT]

Ok. I also tried to prime it by turning the key off and on a few times. It wanted to start for a split second and then back to just cranking.

What’s the trick to putting fuel in the throttle body to try that? Just pour a little to fill it with the throttle closed?

Do it 5-8 times. It needs to be on each time for a full 3 sec so fuel primes the rail. If it falls off it won’t start. So do this 8 times and it should crank right up

 

[FuNkYMoNk85]

Do it 5-8 times. It needs to be on each time for a full 3 sec so fuel primes the rail. If it falls off it won’t start. So do this 8 times and it should crank right up

So I did this 8 times and it wanted to start briefly and just kept on cranking. If I push the gas while cranking it hesitates but still doesn’t start. I have 42 psi on the gauge for fuel pressure.

Also removed and bench tested the crank sensor, seems to be working just fine on the bench. When I back probe it with the key in the on position (sensor removed and in hand) I can bring it near anything metal and hear all the relays open up and I get a change in voltage briefly and then it drops off. I assume this is standard operating?

Just not trying to shotgun parts at it, I’d rather be sure before I buy anything if possible.