Long cranking

I have this vehicle that cranks fast and takes long time to start up on its own, meaning cranking up to 4 seconds before starting. But if I crank and tap on the throttle it fires up normal under the 2 seconds. Sometimes it fires up normal without using throttle. Fuel pressure was tested and no codes new fuel pump due to failure.
V6 93 mazda sentia

Did it have this problem before fuel pump was replaced? If you cycle the key a couple times before cranking does it start better? Usually if opening the throttle helps then its a rich condition i just want to rule out fuel pump before going that route . Also does it do it every time you start the engine or only worm or only cold?

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The problem was there before pump replacement. Sometimes cycling starts it up on the second crank. Only sometimes. Does it both hot and cold. Idles and drives normal once started. Fuel pressure holds after shutoff according to the guage

Have you had a chance to verify that both the egr and iac are not sticking and move smoothly? IMHO, that would be what I would check next. I've encountered similar behavior, and for me, it was a sticking iac.

If those checked out, I would then test spark and injection when hard starting occurs.

Also worth noting that if this vehicle has evap that a stuck open evap purge solenoid will cause this as well otherwise the egr valve is what I would look to next

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Hi..
If you have a scope check your crank sensor, I think you will find that you have little or no sig for a few seconds then the sensor comes alive and starts..

Doc n2mx

I have checked and nothing is stuck open.

I agree with Ben. Tapping the throttle gives a little "gulp" of air. On some vehicles, when the throttle plate is completely closed, air should flow though the tiny gap between the throttle plate and body. When the throttle body gets carboned up, the gap is sealed. This is, usually, accompanied by high IAC counts. Have you cleaned the throttle body?

The throttle was cleaned in the past but it did not solve the problem.

The thing I notice is quick cranking and oil light goes off it will most likely startup

One of the problems with this generation of vehicle is the limmited diagnostics codes offered by the ECU. I don't know these engines but if it has a 2 wire (magneto-resistive) crank sensor that is a possible cause of the problem. So the first stage of diagnosis has to be to attempt determine if the issue is ignition or fuel related.

If the issue is due under fueling then pick a cold morning and spray a small ammount of brake or carb clean into the throttlebody before try to cold start the engine, if the engine starts almost instantly the problem is due to lack of cold start enrichment or other lean mixture issue . NB. don't use Eeezy Start or other ether based starting fluid for this as these can actually cause the engine to fire up without a spark

If the test makes starting even harder then it suggests the engine is getting too much fuel durring cranking so look at the evap solenoid or look for a leaky injector.

If the issue is spark related the cranking time will be unchanged, I would measure the voltage output from the crank sensor while cold cranking. You can use an multimeter with an AC voltage scale.

The odd thing is fuel pressure holds at the rail . At one point I used starter fluid and it fired up. Despite having good pressure at the rail. The cold start valve never fires on this vehicle however it's getting voltage while cranking. Cold start valve works manual

For me that is now putting a question mark over the ECT.

I took a look at the ect and checked resistance cold and hot and then back probe and checked voltage and everything is in specs. So it's odd. I disconnect and try starting all it did was put a check light and same issue. As for the cold start valve should it be firing everytime ?

Low compression?

It's possible I haven't done a compression test. However I notice people used rislone compression repair and it increased compression. I might try it and see at the time I'm so busy to do compression test

I notice when I disconnect the tps the car won't start even with use of throttle.

Do you know if the cold start fires everytime you crank the engine? Or should it only fire up at a selected temperature

Back in the 1980s' the fuel pump relay on a lot of cars was wired via a to the oil pressure switch circuit --- (older engine lower oil pressure).
There should be a by-pass that operates to supply power for initial prime.

I would check to see if this car has a leaking fuel regulator since you need to open throttle. Vacuum fitting would be wet when you pull it to check.