Cranking Time

[CBJeeper]

I just purchased a well-preserved 1990 Wagoneer Limited 4.0 auto, complelty stock with 206K on the clock. I can see that the engine has been maintained well. There are actually no leaks anywhere on this XJ! The engine runs well and the vehicle drives great. My concern is the length of starter cranking time needed to start the engine, cold or warm. It seems somewhat excessive. The battery seems fine and the starter cranks at a good speed. It requires a few seconds of cranking. I previously owned a 1990 Laredo and cranking time was easily half, or less what this Jeep requires.

The plug wires look to be new. I replaced the cap and rotor. The spark plugs appear to be newer. I have not yet checked timing and have not cleaned the throttle body.

Any thoughts?

BTW- Yesterday the transmission would not shift past 1st gear. I followed Cruizer54's steps 1, 2 and 10 and viola!, problem solved! Thank you.

 

[Unclewolverine]

There is lot of different things to try, someone will give you a list, but sometimes it's just one of those things that can develop with no explanation; like a slow 1-2 upshift when cold. Mine has usually been hard to start from day one and everything has been changed except the ecm. But somedays it will fire right on up.

 

[RCP Phx]

Probably the first and easiest thing would be to check the fuel pressure. Do you let the system charge before going to the start position?

 

[Saudade]

Bear in mind a few things.

The Renix ecu has no memory. So when you first go to start it, it has no idea where the crank is located in relation to #1 TDC. So once cranking, the crank needs to reach about 300 rpm in order to reach proper cranking speed. It then needs to get the sync signal from the distributor in order to locate pistons 1 and 6. It can then sync fuel injector pulse with ignition timing and start the engine. If it doesn't get the sync signal, it will randomly select an injector as #1 and use it to sequence the the rest of the injectors. The ECU also needs input from the coolant temp sensor, the intake air temp sensor, the MAP sensor, and TPS.

My '88 take several seconds to light up.

A few things to try.

First, turn the key to ON (not start) and listen for the fuel pump prime. Turn the key off. Then turn the key to ON, then turn to START. Does it start quicker?

Check your fuel pressure. Engine off, key on, should be about 39 PSI. Start engine, fuel pressure should be about 31 PSI. You can also pinch or remove/plug the vacuum line to the fuel pressure regulator. With no vacuum, it should be about 39 PSI.

The timing is not adjustable.

 

[CBJeeper]

I have not been waiting to initiate fule pummp pressure. I will try this sequence and check the results. Thank you all for your valued input!

 

[cruiser54]

Long crank time is absolutely normal on Renix fuel injection. You will never eliminate it. You can possibly reduce it by taking an hour or so and completing Tips 1,3,4, and 5 at my website. www.cruiser54.com.

 

[CBJeeper]

Thank you all for your feedback. This gives me the understanding that I needed. I am now trying to make it a practice to let the fuel pump charge before starting. This does seem to reduce crank time somewhat.