Grumble Start

Also infamously known as the slow start, I think. My '15 TRD OR DCSB 4.0 w/ 50k miles is doing it. The truck is supercharged (stock TRD unit) but has no other engine modifications to speak of.

When I turn the key to start the truck, it sort of grumbles to life. It does not positively roar to life like it used to. It also doesn't do this every time, but definitely more often than not (probably 8 out of 10 times).

Here's a video:

https://www.youtube.com/watch?v=y5XBRQuUgGk

Per the recommendations of several forum members, I replaced/upgraded the OE fuel pump with a Deatschwerks DW200 via URD's fuel pump upgrade kit. No perceptible change before or after the swap.

Anyone have any ideas on what else it could be?

 

hmm. How old is the battery? and have you tried bypassing the fuel pump resistor?

 

Battery is OE.

I don't know about a fuel pump resistor? What is it?

 

I believe Its a grey box down in front of the battery. Unplug and take a piece of wire and jump the two pins together

 

What tune do you have?

 

I think I'd start by putting a fuel pressure gauge on it and verifying fuel pressure doesn't bleed off when the engine is turned off, it should hold at least 21 psi for at least 5 min after the engine is shut off, if it doesn't you have a bad check valve or leak at the pump or a leaky injector or fuel pressure regulator.

 

What am I looking for when doing this?

JustDSM's S/C tune via HP Tuners. I've been in touch with him. He verified it wasn't anything in the tune itself. I even flashed previous versions of the tune to confirm it wasn't a glitch in the latest one.

I've had a fuel pressure gauge plumbed into the system to see what's going on. With the engine running, it holds steady at 42psi. Upon shutting the engine off, it holds well over 21psi for well over 5 min. It does gradually go down but over the course of several hours.

 

Our trucks have a 2 speed fuel pump, the resistor provides low speed via the fuel pump relay at idle and under low loads.
I wouldn't expect it to be that since I'm pretty sure that it always starts with the pump on high speed but you can try it and see if it makes a difference, are you getting any trouble codes?
Picture's borrowed from @Jimmyh.

 

OP if you turn the key to run, dont try to start it, wait 5 secs, turn to off, turn to run again, wait 5 secs then start does it grumble to life or start like it should?

 

Just tried that - no noticeable difference.

I'll check out the fuel pump resistor now!

 

Hmm, getting virtually no resistance (checked with two different meters):



Also, just checked for codes using

$27 ANCEL AD310 Classic Enhanced Universal OBD II Scanner Car Engine Fault Code Reader CAN Diagnostic Scan Tool, Read and Clear Error Codes for 1996 or Newer OBD2 Protocol Vehicle (Black)

this scanner and saw no stored or pending codes.

 

Whoops, I think I wasn't waiting long enough to let the multimeter 'settle' on a resistance value. I discovered this after I picked up a new OEM fuel pump resistor today and thought it was also measuring zero. After several seconds it climbed to around .7 ohms.

So it would seem my original resistor might actually be fine.

Any other ideas?

 

Make sure the throttle body is clean an do a relearn afterwards. Another thing to check for is a dirty MAF

 

For these value of resistance, you need to take 4 wire sensing measurment (https://en.wikipedia.org/wiki/Four-terminal_sensing). I don't trust anything cheap for these low value. The last digit can be off +- 5 (or more) and you add a % error over that. They only say Basic DC accuracy ±0.5% error on the site for your mm200, this is mostly useless since they don't say which range this is true (and they will probably write the best lab result they can do in a controlled enviroment @ 25c).

.2 ohm difference is alot at these small value.
12v @ 0.7 ohm is 17.14 amp.
12v @ 0.5 ohm is 24 amp.

V = I * R

Like you did trying a new resistor is a good idea but if you have corroded wire or a bad connection on the path this can affect the performance greatly. If you can measure the real resistance with a good meter and measure the voltage between the 2 pin of the resitance when the pump is working you can calculate the current flowing in the circuit. You will know if the pump work correctly. The "bad wire" will add resistance on the circuit and this will lower the current flowing in the path.

 

I don't really see a problem in the video. It starts the same amount of time any other Tacoma does. Am I missing something here?

If the battery is OE that would imply it's over 6 years old at this point. Replace that sucker.

 

I used to have the slow grumble start where people riding with me would ask if there was something wrong.

Knock on wood...once I ditched the Toyota battery and went with a higher CCA aftermarket battery, it rips and fires better than ever.

 

Brand new Odyssey 27F battery installed. A good 13lbs heavier than stock. Zero change in the starting hesitation.

 

My truck did this for 6 months and then the battery finally went.

New battery…now it fires up as fast as I can blink.

 

So a very strange thing happened starting about a week ago. All of a sudden, out of the blue, the problem is gone. Truck roars to life with authority. I can't get it to NOT confidently start anymore, even if I let it sit for several days or more. And the new battery has been installed for a while now, so I'm not sure what the deal is... but I'll take it.