Warm hard starts, test or just replace FPR?

[rationull]

I've got the fuel rail off our 1999 454 Suburban while I'm changing the intake gaskets. The truck has trouble starting when it's warm. Have it warmed up, turn the engine off, wait 15 minutes and try to start it again, it's gotta crank way longer than normal (probably ~5 seconds) before it fires. Driveability is fine, no fueling problems while idling or running AFAICT.

From my reading, this is generally caused by either the fuel pressure regulator or the injectors. I was guessing the FPR, both because it's the first thing I read about, and also because the problem isn't really that bad and the injectors are more expensive and more of a PITA to replace I would think (this vehicle is not a daily driver).

Is there anything I can do to test either the injectors or the FPR while the rail is off the car? If not, I'm tempted just to replace the FPR even though it feels a little like shotgunning the problem. I'm sure not going to replace the injectors without good reason though.

Anything I can just inspect even? If I open up the FPR, will any malfunction be obvious or do the diaphragms just "stretch out" or something that might not be noticeable on inspection?

 

[yonyon]

With the rail off the car you should be able to see any leaking injector. Cycle the key a couple of times to be sure you've got pressure and look for fuel.

 

[rationull]

Huh, I hadn't even thought of hooking it back up, connecting the battery, and looking for leaks. Go figure. Only downside is that it would re-pressurize the rail and result in a little more fuel leakage if I have to take it back off.

 

[jetmech1]

Quote:
With the rail off the car you should be able to see any leaking injector. Cycle the key a couple of times to be sure you've got pressure and look for fuel.


+1 Sounds like you got several injectors leaking down and basically flooding the engine. Here's another option if you find some of them leaking.

Here's a link to a company that builds specialized machinery to test and clean injectors. If you live near a large enough city, some better shop may have one of these or someting like it. Then you can have all them thoroughly tested. There's a diesel shop near me that has one that does it real reasonable. They can clean them up and get them working like new most of the time.

ASNU Fuel injector service

 

[CharBaby]

I have a very similar situation in my '04 Altima 2.5. But it only happens in the warmer temps, namely summer time. All autumn/winter and most of the spring time it's fine. It's been doing this a couple of years now although the car runs fine!

I can usually plan on it doing this(longish starting issue) when I am doing lots of running around town with frequent restarts. Left unstarted for several hours, it's fine here too!

If I think the engine is going to take long to start when I get in the car, I'll cycle the key/fuel pump 3X's and it'll start normaly. Not that I want to be doing this for the rest of the cars life as I'd really like to find the actual cause and fix it. But for now, this is my way of masking the problem.

I believe that I have even discussed this particular matter with a fellow BITOGer/ex-Altima owner and we came up with...

Injectors leaking down

or

Fuel Pump Regulator

 

[Trav]

Hi rationull,

I can test the injectors and clean them, i have been doing it for a long time and have all the right equipment including the ASNU machine.
Check my sig.

 

[JosephHarmon]

Many GM's have a presuere switch at the oil filter or nearby the has four wires going to it. Two wires function the low oil pressure lamp & the other 2 wires complete the fuel pump circuit. Replacing this switch solved my long cranking issue. It was about $12.

 

[Brons2]

Originally Posted By: Trav
Hi rationull,

I can test the injectors and clean them, i have been doing it for a long time and have all the right equipment including the ASNU machine.
Check my sig.


Don't think the board rules allow that unless you are a site sponsor. I'm surprised the owner hasn't removed the link. She removed my link to my gas mileage at Fuelly, which surprised me, but Fuelly is not a site sponsor, and rules are rules.

Anyway, I would check with Helen (I think it is?) before advertising your services.

[edit] on a side note, your website is great! very informative.

 

[Samilcar]

Trav is a site sponsor.

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2191291#Post2191291

 

[rationull]

Thanks Trav. I'm not 100% sure if I'm going to touch the injectors at this point. The problem isn't really a big deal to us given the amount this vehicle gets driven, so I might just throw on a new FPR as a gamble without even taking the injectors off the rail, unless I can find some evidence the injectors are leaking.

I would think with leaking injectors we'd see a big puff of black smoke after cranking when it finally started, wouldn't we? No smoke AFAIK.

 

[ltslimjim]

Warm/heat can also be electrical parts, does this car has a main fuel relay to listen for if it clicks normally(like on a cold start) but changes behavior on warm restarts?

Sometimes heat can indicate a failing ignition component as well, but usually that results in stalling. Can you hook up a test gauge to the fuel test port and get pressure readings with Key On Engine Off?

 

[The_Eric]

Originally Posted By: rationull
Thanks Trav. I'm not 100% sure if I'm going to touch the injectors at this point. The problem isn't really a big deal to us given the amount this vehicle gets driven, so I might just throw on a new FPR as a gamble without even taking the injectors off the rail, unless I can find some evidence the injectors are leaking.

I would think with leaking injectors we'd see a big puff of black smoke after cranking when it finally started, wouldn't we? No smoke AFAIK.


Not necessarily. We had a 454/7.4 in the shop with the same problems, that ended up being the injectors. By looking at the pipe, you'd have never guessed.

To check the FPR for obvious problems, look down inside the vacuum reference tube. If there's fuel in there, it's definitely bad.

 

[Trav]

Quote:
would think with leaking injectors we'd see a big puff of black smoke after cranking when it finally started, wouldn't we?

That's one possibility but many i see just have a very slight drip when under full pressure, usually no smoke will be noted if this is the case.
Either of these scenarios is not likely to be the cause of a hard start condition unless one was stuck wide open, then you would certainly notice you have a major problem.

A very common and more likely issue with GM injectors of this era is plugging or reduced flow, this will cause hard starting.
This is common in engines that don't see a lot of road time and may have fuel sitting in the injectors for an extended times, this is further accentuated with the use of ethanol laced fuels.

It is not uncommon to see a 30-40% increase in flow with these units depending on their condition after cleaning.
It seems from my observations anyway that the smaller metal bodied Bosch units are more prone to this internal corrosion than the longer and thinner plastic bodied Delphi ones.

IIRC your FPR has a vacuum hose, check for any fuel being present at the hose when you take it off, if none is found the units seals are in good condition.
Do a pressure test at the test port with the engine running and pull the hose on the FPR again, the pressure should increase. If it does the FPR is functioning properly.
Make sure your fuel pressure is within specs. Change the filter, a partially clogged filter will alow pressure to build but reduce flow.

 

[rationull]

The filter's only been on there for probably 4000 miles (although it's been a few years to be fair). This car does sit for a 2-4 weeks between uses generally and only sees 10% ethanol fuel.

Now I'm wishing I'd done more diagnosis before taking this thing apart. I didn't get any fuel out of the FPR's vacuum hose when I pulled it off, but I'd already disconnected the fuel pipes so it's possible whatever was in there would've drained off by that time.

I'm trying to walk the line here between doing something that might fix this problem and ignoring it, because it's an annoyance but not really a problem. If I get this back together and the LIM repair actually works out, I don't think I'm gonna pull the upper manifold off again just to fix the hard start, so any more diagnosis with the engine running is probably not going to result in a repair.

I will reconsider though, and maybe it'd be worth it to get the injectors cleaned *and* replace the FPR just in case. Any electrical problems could be dealt with after putting it back together.

 

[Trav]

Do these injectors have a steel body with 3 nozzles on the bottom?
If you are considering cleaning i wouldn't bother i would just replace them with the deal that is on them right now. Standards are on close out at Rock Auto. They are new not remans and at $31 each are a great deal, these are $75-100ea all day normally!

Don't wait to order these they will sell out fast! The part# is FJ241

 

[mechtech2]

Originally Posted By: rationull
Huh, I hadn't even thought of hooking it back up, connecting the battery, and looking for leaks. Go figure. Only downside is that it would re-pressurize the rail and result in a little more fuel leakage if I have to take it back off.


This is a hidden irritation by GM!

For the OP:
A temperature sensor is #1 on my list for the given symptoms.
You have enough pressure cold, when you need MORE gas, so other things are probably OK.
Leaky injectors would show themselves on a COLD start, after they have had MORE time to leak.

 

[rationull]

Originally Posted By: Trav
Do these injectors have a steel body with 3 nozzles on the bottom?
If you are considering cleaning i wouldn't bother i would just replace them with the deal that is on them right now. Standards are on close out at Rock Auto. They are new not remans and at $31 each are a great deal, these are $75-100ea all day normally!

Don't wait to order these they will sell out fast! The part# is FJ241



From the picture rockauto.com they look similar but my injectors have 6 holes. Here's a pic of the bodies:

Originally Posted By: mechtech2

For the OP:
A temperature sensor is #1 on my list for the given symptoms.
You have enough pressure cold, when you need MORE gas, so other things are probably OK.
Leaky injectors would show themselves on a COLD start, after they have had MORE time to leak.


I don't know much about this at all but it seems like I've read plenty of places where people have had this starting issue only when warm on Chevy trucks and either the FPR or the injectors was the cause. Would a temp sensor issue not cause drivability issues along with starting issues?

 

[Trav]

The 6 hole style is more prone to plugging due to the smaller holes, i would probably clean them its cheaper than pulling the upper off again. At least you will be able to eliminate them from the equation.

 

[ltslimjim]

Trav, on the subject of injectors. Can an injector make more noise with age, like on my old Civic, from the gaskets and seals/o-ring degrading; perhaps enough to cause issues with flow?

My car has a FPR, and a serviceable fuel pressure test location via the top screw into the firewall mounted fuel filter, the hose from this location feeds the fuel rail/injectors with the FPR on the backside. I've never done the KOEO test for the pump's ability to build pressure vs the FSM, nor the FPR's vacuum line disconnect to inspect/smell for gas post FPR(the vacuum line to the IM?).

I notice my injectors are noisy, typical you know, but some sound a little different in loudness(not necessarily ticking pattern) than the others. I've wondered if it could simply be the sealing rubbers/gaskets instead of automatically assuming a clogged injector.

I ask as well because similar to the OP, I also have warm restart and warmer weather issues(aside from a suspected 'bad' IACV or ignition components on a 20 year old car once up to temp) I get some hesitation/delays but no cutting off etc, at times on warm restarts. It's either a sensor, ignition, air/fuel mixture; and their sources, or mechanical/internal issue.

Trying to learn more about fuel deliver in that equation and the symptoms by ear, such as what a 'mechanic stethoscope' on injectors without having to pull the fuel rail, might indicate from sound given the age of a vehicle. Could injectors be more noisy than neighboring cylinders and it 'not' be a flow issue?

 

[Trav]

Noise is not really a good indicator of anything, some are just noisier than others.
I see both quiet and noisy ones have flow problems, there doesn't seem to anything in the noise that you could conclude one has better flow than the other.

Seals and other replaceable parts in the injector will have no effect on injector noise, i wouldn't give it a second thought especially if all have similar noise, if one was much louder than the others i would probably replace it (cleaning will not help).
Do a KOEO pressure test, remove the vacuum hose to the FPR and look at the change than compare to specs.
Fuel at the FPR vacuum connection is always ground for tossing the FPR regardless.
Raw fuel will bypass the injectors and go right down the intake through the vacuum hose, the O2 will see this as a rich mixture and try to lean out the injectors.
You will see a higher minus number on the scanner, only if this goes over +/-16 it will trip a code and CEL in most cases.
A slight drip can keep it well below -16 and no CEL.

ECM temp, MAP and MAF sensors can all cause hard starting, these usually cause a CEL if they have a hard fault but i have seen them not just as often.
I did a Ford recently that had bizarre barometric readings all the time and it made adjustments for that (Boston is sea level) no CEL.
Changing the MAF sensor fixed it.