bravada wont start when warm

I will try to make this short..
I have a 1999 olds bravada, been kind of running rough.. missing alittle when driving. Now a bigger problem. I can start it, and it runs great, problem is.. when I shut if off it wont start. turns over fine, and has a brand new battery.
Sounds like it's not getting gas(even tho I can hear the fuel pump running). After it sets about a half hour it starts right back and runs great untill I shut it off again.

The first, and easiest thing to check is spark. Do you have good blue, (not orange) spark at each spark plug when it will not start?

yeah getting spark

Check fuel pressure and leakdown. Ignition ON, engine OFF, fuel pump running: Must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off.

thanks for the help... I did check fuel pressure.. it was holding about 60 psi.

This problem is a couple weeks old, i tried about everything I know of and more. Any help is VERY apprciated

Is there a security system installed on the vehicle, factory or aftermarket? Security systems typically disable the fuel injectors. The vehicle has passlockII from the factory and it's possible it's disabling the injectors. If it's a passlock problem, the security light should be ON.

No lights like that only check engine light is on.... but i probably should have mentioned this earlier... Service engine light comes and goes. only trouble code is PO300.
I understand this is random misfire on multiple cylinders. But the problem with that code is it could be literally a dozen things.

All P0300 series DTC's are almost always caused by secondary ignition faults. They include spark plugs, spark plug wires, distributor cap, distributor rotor and the ignition coil. The 4.3L engine is very fussy when it comes to ignition parts. Aftermarket parts do not perform well, especially when it comes to the distributor cap, rotor and spark plugs. Best to stay with AC Delco on those parts.

There is a TSB concerning the vents in the distributor housing being clogged, which will set a P0300 DTC in memory and turn the SES light on. Condensation forms on the underside of the cap and it can not be ventillated if the vents are clogged. The TSB instructs you to remove the vent screens completely and to replace the distributor cap and rotor. Use a dab of silicone dielectric grease on each terminal, (inside and out) of the cap.

would any of those cause the "no start when warm" condition?

Absolutely! If/when condensation accumulates in the cap, when you try to start it after a short hot soak, the spark jumps all over inside the cap, causing a no start and in some cases, setting the P0300. The warm, moist air inside the engine rises up past the distributor bushings and condenses on the under side of the cap. After it dries out, it starts right up.

Update.....

Checked the distributer cap this morning, it seems to be OK. I really dont think its gonna be a firing problem, because it does fire when in "no start" condition.

I beleive its going to be in the fuel system. When it wont start, its not getting any fuel. I can put a little in the "carb" and it will start. Shuts right back off after that fuel is gone. The fuel pump is still working, Im just not getting it to the carb.

another note ...The security light does come on after i turn the motor off, it flashes for a couple of minutes then goes off. but it has always done this. I dont know if this has anything to do with my problem(im looking at passlock posts now)..
I am getting good fuel pressure up to at least the fuel rails, but not to the injector

Another update:

Disabled passlock(got the info from other posts, thanks all)
No change, ran it about 20min, ran perfectly. shut it off wouldn't start back.
Wait 10-15 min starts back run good again.

*security lights flashes after I shut off the motor.
*getting good spark
*getting fuel to fuel rail, not to "intake"

Make sure the pink wires to the injector pack have battery voltage when the ignition is in the RUN and START positions. The ECM supplies a ground signal sequentially to each injector to energize it.

not to sound dumb, but where is the injector pack?

Just behind the throttle body you'll see a black plastic cover. Under that cover is the electrical connector for the injector pack. There are 6 mini injectors in one housing. Each injector has a line that runs to each intake port.

Ok, I checked the the injector pack (thanks for telling me how to find it.)
I got 12 volts in the "start condition"
and 12.5v in the "no start condition"

I really appreciate your help, you seem to be very knowledgeable. Do you have any other suggestions I might be able to try?

I got some new info... I retested the fuel pressure, it is fine
When I start the bravada the pressure INCREASES by about 10psi (I didn't test this before)
After researching I found out that the fuel pressure regular is bad
the regulator from what I understand, can cause my problems. I am going to change it in the morning and post what I hope to be, good results. wish me luck

I found a bad Ignition module, when the engine was cold the timing was OK, when the engine got hot it would lose timing.
I took the ignition module out and Advance Auto tested it as being bad.
A new ignition module resolved the problem.

did you have the same problems I have? run good, wouldnt start after I turned it off

Run good cold, and wouldn't start when hot.

having a brain fart... is the ignition module the coil?

The crankshaft position sensor tells the ECM where the pistons are in crankshaft rotation. The ECM gathers data from other sensors and calculates when to fire the ignition module. Ignition timing is controlled by the ECM, not the ignition module. The ignition module fires the ignition coil, and the distributor sends the voltage to each spark plug.

Ok fuel regular Was NOT the problem.
I checked fuel pressure when it wouldnt start, getting about 20psi
So I guess it is probably the fuel pump, right?

Something is intermittent, could be electrical or possibly the fuel pump itself. Diagnose it correctly before you replace anything. Check your inbox, the PM explains exactly how to diagnose the fuel delivery system.

Something is intermittent, could be electrical or possibly the fuel pump itself. Diagnose it correctly before you replace anything. Check your inbox, the PM explains exactly how to diagnose the fuel delivery system.

thanks for all the info, might take me a bit to go thru it all.. appreciate it

Thanks for all that info here is what I found out:
Fuel pump activation......works fine
fuel pressure test..........60psi 57psi while running
fuel leakdown test..........60psi-no leakdown
test max out put... I dont have the tools

You mentioned it might be electrical. I can hear the pump kick in when It wont start, but Im getting very low 20psi fuel pressure.
I would apprciate any more help you might be able to offer.

Fuel pressure with the key on, engine off, and the pump running, at 60psi is at the bottom end of the spec, could just be a weak pump.

Intermittent low fuel pressure could be a number of things.
Worn bushings in the pump motor
Worn brushes in the pump motor
Poor connection at the pump motor (inside the tank)
Poor connection between the fuel pump relay and the pump module
Poor fuel pump ground
Poor connection in battery feed to the fuel pump relay

Something to check for the last 4 items would be to unplug the connector at the pump module and check battery voltage on the grey wire with the key in the RUN and START positions, should show battery voltage in both positions. Check resistance to ground on both of the black wires in the module connector, should be less than 5 ohms.

There are some things to check ;)

is there any way to get to the pump module wiring without dropping the tank?

Also I dont know if this would mean anything, but every since ive been having problems I only keep a little gas in the tank(figuring i was going to have to replace fuel pump).

You don't have to remove the tank, but you'll need to drop it down far enough to get at the connector. The pick up is very close to the bottom of the tank, obviously if it's sucking air, it's not going to start. ;)

Most of those problems you told me about involved the fuel pump.. If i was going to do that, do you think it would be a good idea to go ahead and change the pump?

OEM fuel pumps are typically good for about 100,000 miles, anything over that, consider it a bonus. With that in mind, if you can't confirm a problem with it, consider the mileage. If it's close to, or over, I'd replace it simply because it's bound to fail shortly, and the tank is down anyway. If you do replace the pump, do yourself a huge favor and use AC Delco or Delphi. They do cost more, but it beats doing the job again in a couple of months.... when it's cold outside. So, bottom line, take my advice and do what you want ;)

I really do appreciate your advice, I hate to keep asking but before I spend 300 on a fuel pump. Do you think that is likely to be my problem?

oh... there is 135k miles on it

...I can hear the pump kick in when It wont start, but Im getting very low 20psi fuel pressure...

This could be an important clue but, like I mentioned, it could be a poor electrical connection causing it. The electrical connector at the fuel pump module is a known problem area. If the connection loosens up from vibration while driving, the terminals get hot from the high resistance and melt the connector. Also, as the pump motor wears, the motor draws more current and the higher amperage draw creates heat and adds to the connector problem. It also causes the motor to wear faster contributing to its own demise. Eventually the connection burns to the point that the motor can no longer get battery voltage and quits totally. Replacement fuel pump modules come with a new style connector. They supply crimp connectors for splicing the new connector to the existing vehicle harness. DO NOT use the supplied connectors. Solder the connections and use heat shrink tubing to "weatherproof" the connections.


The fuel pressure spec for the CSFI engine is 60psi to 66psi. The poppet nozzles at the intake ports require 40psi before they will open and squirt fuel so anything less than that, the cylinders will not receive any fuel. Typically on a cold engine, if fuel pressure drops below 60psi, it will be hard to start and there will be performance issues when it does run. If fuel pressure drops below approx 55psi, you can usually get it to start by spraying some carb cleaner in the throttle body, but again, there will be performance issues when it runs. If fuel pressure drops below 50psi, even the carb spray might not get it running.

If the fuel pump is original at 135,000 miles, an "educated guess" would be that a faulty pump is what's causing the problem. Bottom line is that without a complete diagnosis, it's a $300 guess ;) Hope this helps.

yes that does help.. I am going to drop the tank today to check the connections. I will let you know what I find out

the electrical connections seem to be fine. they were very tight, and clean. I didn't see any burnt spots or any signs of heat.

When you got the 20psi reading, was that while the engine was cranking? And did the pressure remain steady at 20psi?

20 psi key on NOT running no increase in PSI when cranking... yes it stayed there

Sure sounds like it's the pump. Do you have any trouble with the fuel gauge not reading correctly? Have you had any EVAP DTC's showing up? The fuel level sender and the fuel tank pressure sensor both come with a new module. If you're not having fuel gauge or EVAP DTC's, you can replace just the pump and it's a ton cheaper. You can get an AC Delco pump repair kit on eBay for around $60. All you get is the pump, no module housing, pressure sensor or level sender.

no I dont have any problems with fuel gauge, or any trouble codes.. I will have to check out Ebay, 60 is alot better than 300. I really appreciate your help and I will let you know how changing the pump works out.

I'll be crossing my fingers ;)

Ok I got a AC Delco fuel pump.. But I cant seem to figure out how to get the other pump from the sending unit. I unclipped the power wires and got the two clips on the side of the unit. Acts like something else is holding it in. Any suggestions

Did you remove the sock, (filter) from the bottom of the pump?

yes, that was the first thing I did. Looks like maybe a fuel line that connects to the top of the pump

The "accordian" looking tube is the pressure line from the pump, yes, that has to be removed.
There may be a clip or clamp on the rubber insulator that the motor is mounted in, can't remember for sure.

Ok got it apart. Gonna install it in the morning. Will post back my results

See post #42

Well... that didn't work either. Same problems no better at all. I really don't know what else to do. Any ideas?

Ok, lets go back to my first reply and dig a little deeper. "Are you getting good blue, not orange, spark at every spark plug when it will not start?" Also, as I mentioned earlier, P0300 is almost always caused by a fault in the secondary ignition system. There are other things that can cause it, such as the MAF sensor, low fuel pressure, and sometimes a TP sensor. Those may or may not set a corresponding DTC in memory.

How many miles on the distributor cap and rotor? Do you know what brand they are?
How many miles on the spark plugs? Do you know what brand they are?
How many miles on the spark plug wires? Do you know what brand they are?

Excuse me gentlemen, I've been following along and agree with the dialog so far.
What's the fuel pressure now with the new pump when you first turn the keyswitch on?

Good call, Chris!

UPDATE:

I checked the fuel pressure and was getting zero psi, I took the fuel line off the fuel filter, no fuel. Then I dropped the tank figuring I may have got a junk pump (new AC Delco from Ebay)

When I removed the pump, the problem was obvious, the fuel line "popped" off from the pump to the sending unit. I put it back on, this time with clamps (none were provided with kit so I didn't think it needed it).

I have run it the last couple of days and it runs really good (knock on wood). I have the same fuel pressure after an hour of running as I do when it's cold. I will post back if anything changes.

Big thanks to Chris!

The fuel pressure regulator keeps pressure in that hose from rising above whatever pressure the regulator is set for, usually around 62psi. Continuous operating pressure of the pump is designed for 61.64psi and maximum output pressure between 72.52psi and 108.78psi. The only time that hose should see anything above regulated pressure is when testing maximum output pressure. So, yes, it needs to be clamped on securely at both ends.

What is the fuel pressure with the new pump?

A Huge thank you to old master, and you too Chris. I would have never figured this out on my own. This is a great site.

Oh, my fuel pressure is about 63psi

Beautiful, thanks for sticking with it and for posting back the fix.

Thanks for the update and here's one to our pal, Old Master.:cheers: