The car: 90 Bonneville SSE.

Problem: Wouldn't start last week, no fuel pressure. Replaced fuel filter (was in backwards, plugged), runs fine again.

Until this morning. Won't start, no fuel pressure again. Buy fuel pump and strainer, filter still okay. Replaced fuel pump (AC Delco), two hour job, now have good pressure.

Still won't start. Mighty fart out of intake or exhaust occasionally, but won't fire.

Pull plugs. Soaking wet. Spend next two hours drying everything out and crank on it some more. Check spark, fine (plugs & wires ~3 weeks old). More farting and coughing. Finally starts. Runs fine after a few seconds of stumbling.

Clean myself up, take wife & son to dinner, runs fine, starts fine.

Can a weak fuel pump cause a cold FI engine to "flood"?

 

Just an "educated" guess here but i'd assume the low pressure would cause the fuel to not atomize/spray correctly, if at all. If the fuel doesn't atomize it won't evenly mix with the air and form a combustible mixture. Obviously if the fuel from the injectors is just dripping into the chamber when they fire, it wouldn't seem out of the realm of possibility that the engine would flood....

Just my .02.

 

regulator and injectors ok ? i sure don't know much about FI but if you have a preasure drop and you replaced the fuel pump that's about all there is left to look at.

 

The low pressure only existed with the old pump (and old fuel filter). It's fine now (don't have gage, just judging from the squirt when pressing the Schrader valve).

These Bonnevilles are the only FI I've ever had. Nice system, but some of the "old school" conventions don't apply. Air/fuel/compression/spark still do, though.

 

Well, I spoke too soon. I didn't check for fuel pressure before I turned the key, but it was hard to start again this morning. After it started the first time, no problems starting it the rest of the day. It does run better with the new pump, though.

That leaking fuel injector suggestion is sounding more plausable.

 

if after you put a new pump in and then you are flooding out the car prolly just have the built up pressure within the fuel system leaking into the motor due to leaky injectors.
also that will cause the car to run kinda rough as was already stated b/c the fuel is not going into a mist but just globs.

best thing to do is take them out and replace them or send them out to be clean
www.rceng.com will clean them all blueprint them and balance them for you

 

cruzin preformance will clean and flow match a set for a v8 for around a 100 dollars. if you don't mind waiting while they're being shipped, or want to pay for overnite then they may be a good deal and fix your problem.

 

take a look at the fuel pressure regulator vacuum line and see if its got gas in it-sometimes the diagfram (how do you spell that word?) will pinhole and allow raw fuel directly into the intake tract causing like you described

 

Before turning anything on this morning, I checked for pressure at the Schrader valve - nothing. Pulled the vacuum line from the regulator - dry. Turned the key to on - pressure at the Schrader valve. Went to start it - acted flooded again, but did start (kept it floored until it coughed the first time, it started soon after that). Since then, it has started and runs nicely for the rest of the day.

So, it does indeed sound like the injectors are leaking into the manifold. Since this started at about the same time as the filter plugged, I'm going to try a healthy dose of gasoline detergent and see if that helps to clear it up. If not, looks like the injectors are coming out.

Thanks for the ideas. If anyone has anymore not yet mentioned, don't hesitate.

 

i think that the 3.8 has a gm maf sensor-just for sh-ts and giggles unplug the electrical connector to it tommorow and see how the car behaves upon start up. losing fuel pressure overnite is fairly common-although im not saying leaky fuel injector(s) arent the cause of the symptom-you could check how long the system holds pressure after shut down too-if it bleeds off in less than an hour there is a leak somewhere-then we can start clamping fuel lines to determine just where it is

 

Too late for today, perhaps tomorrow.

It used to maintain fuel pressure overnight. I know this, because I also have problems with our '91 Bonneville being hard to start (it doesn't maintain pressure, either, but takes three tries before it starts, whether cold or hot. I suspect the Pep Boys fuel pump on that one).

 

Injectors are likely your problem. My buddy had very similar problems on his olds...After the injectors were replaced the problems went away.

-peace

 

Update:

Full set of injectors (new), absolutely no difference.

Co-worker with 1-year-old Mountaineer wouldn't start for his wife while he was on business travel. Towed to dealer, they re-loaded PROM (no particular reason - just something to try), problem persisted. They told him to try not to use alcohol-oxgenated gas, hold it to the floor if it doesn't start and floods.

It can take a good 20 minutes to get this Bonneville started. Not good for starter, battery, alternator, oil...

 

So you're engine is flooding after it is turned off? Are you getting any check engine lights? A faulty ground wire could cause a lot of havoc, I'd check that out. Have you replace the fuel pressure regulator? Dirt and crap can get in there and I'd guess it can cause troubles as well. Have you tried pinching off the fuel return line after the car is shut off, and checking for pressure a little later?

 

stop stop stop throwing parts stop stop stop-why isnt it starting? need answer this isnt repair this is guesswork of the best guess kind-no fuel? try spraying carb cleaner in the intake thru a p.brake fitting in the am.fuel pressure bleeding off? clamp off a supply line one night and ck for residual in a few hours-then the same with the return-start narrowing the focus here by methodically reducing the things it CANT be. do you understand this approach will get you to the cause of the symptom you desribe. knew f.injectors would be around the bottom of the list for a culprit here. the approach taken up till now is called the "shotgun" approach and is used by people w/o the desire to really learn about cars inner workings. whatcha do is this;load up the ole pasrt shotgun with everything ya got (and some ya dont) and let er have it with both barrels. un acceptable way to kill the cockroach thats boggling you. i think i am the only one who hasnt said replace part xxxxxxxx(fill in the blank) figger it out first. man this pisses me off stop buying parts. go* dam*t

 

Well, in order: No codes since TPS (before the problem started). The filter was definately plugged, so replacing it wasn't a shot in the dark. The fuel pump was definately bad, so replacing it wasn't a shot in the dark, and strainer goes with the territory. Earlier, the TPS was definately bad, so replacing it wasn't a shot in the dark. O2 sensor, plugs, wires are standard tune-up items (plugs didn't look so hot). One of the reasons I replaced the injectors was a last-minute trip to Montana to pick up the mom-in-law at the beginning of the month (didn't want any touble on a 1600-mile trip in the middle of winter - started hard in the cold, outside-all-night morning, but otherwise not a hint of a problem. The car has 135k miles on it, BTW).

I have checked pressure an hour after shutting off, 4 hours after shutting off, 8 hours after shutting off. It had pressure at least 4 hours after. It has started w/o problem as long as 6 hours after last being run.

Since the reg allows pressure back to the tank, a bad one isn't going to flood the intake overnight.

As for lack of diagnoses, you suggested unplugging the MAF, Grump, but didn't give any clue what doing so would or wouldn't do and/or indicate. Want to expound on that?

Furthermore, "replace parts first" is hardly my MO. I've made my living as a failure analysis engineer, for pete's sake. But, lacking blueprints, specs, and full-up test equipment, I'm here to learn and solve. So, I do appreciate the input/suggestions/ideas/etc. Before I take it to the dealer and pay $85 to be told the same thing as the co-worker...

 

To expound on the TPS issue:
Was getting a code that said "TPS voltage low" from time to time. With AutoXray, idle voltage was ~.41 (forget exact value, but below .45 for sure), WOT <4.0 VDC. With new TPS, I set idle to .49 (still using AutoXray), WOT was now >4.5. Doing a search on these boards, I see idle should be .54 VDC (seems to be a standard, regardless of induction type).

Any slim possibility that the TPS voltage being low by .05 VDC is contributing to this problem? Again, starts fine when warm.

 

GGA,

Excellent advice about not changing parts without some diagnosis. But 5-7 has been around here and tipped his hand enough to have proven he isn't jsut a "parts-changer". He's more of an analytical type that wants to know the "Why" before the "What Next". But I;m sure you've seen lots of examples of the parts-changing approach to troubleshhoting, so it's always a good reminder.

- - - - - - - - - - - - - - - - - - - - - - - - - - - -

5-7,

As for the leaky injectors, as they say in the "family" - "Forget about it". If you're holding pressure after four hours, it isn't an issue - at least not like the typical leaky injector phenomenon. And you're dead-on with the regulator synopsis - leaking back to the tank only means a little more priming time. It would be good to get a pressure reading, however, to make sure the setting is correct and the egulator isn't failing in another way. If you can get your hands on even a refrigeration guage set, you can test the pressure precisely - just clean and dry the hoses afterward.

As for the theory about ethanol-blended fuels, that just yells volumes about the originator's lack of understanding about the subject. I've been using 10% ethanol since 1976 (NOT a typo) with no problems down to -42°F, and in everything from 2-stroke snowmobiles, chainsaws, lawnmowers, outboards, carbureted and injected auto and truck engines. Even the people that made your engine say 10% ethanol is just fine. I'll bet that the person who said that is the same one who will dump in four bottles of DeMert's HEET in the cold weather instead, and that is methanol - the absolute worst kind of alcohol you can run through an engine.

I'm guessing you have the non-adjustable TPS, right? If so, you can still test it. The ECM will presume the throttle is fully closed and compensate for whatever the baseline voltage of the TPS is at startup - as long as it is BELOW 1VDC. You can check that to be sure, and if the voltage is over 1.0 VDC you may have found your problem.

You may also have a MAF AND a MAP sensor (this IS a 231 Buick, correct?) so unplugging the MAF may not force backup fuel mode.
In 1990, on the 3.8L Buick V-6 in Chevrolet/Pontiac/Canada products (CPC) the control system switched from the analog Bosch to AC/Delco FM MAF on high-performance engines only. All other 3.8L and V-6 engines used speed-density systems (MAP only).

Remeber that the coil packs on these engines are a little suspect - O.K., they're downright crappy. Don't overlook weak spark.

And try to get a fuel pressure reading, please.

 

ok 5-7 sorry didnt mean no harm, and definitely didnt mean nothin personal just wanted to slow the process down to something more methodical-but you are correct, it does seem that majority of parts replaced were bad or under suspicion- but i noticed a certain lack of info on the parts that were tested .hate to beat a drum here but these bonnie with 3.8(it is a 3.8,isnt it?) have a few weak areas that will cause the condition described here is the drum-ac delco factory recommended plugs are almost a mandatory-hate that fu--ing word-requirement in these motors- the symptom you have is also addressed in a tsb and an updated prom is required. what is the 8th vin character? more on weak points-cam sensor is always gonna make me wonder on these motors even factory delco replacements-coil packs ohm em out hot and cold. is cold start the only time the problem shows? check spark with a tester homeade or otherwise. i gotta go again and earn some cash but will get back asap

 

90-6-14 gm tsb concerning this very problem-gotta go- is it a california car?

 

Thanks for sticking with me, guys.

Okay, down the line again:
TPS mount screw holes are slotted, so it can be adjusted. If anything, it's below .5V now.
8th VIN character is "C" (same as my '91 LE). Swapped coil pack & ignition from the '91 (same listing), no difference ('91 started a little easier, though), swapped them back.
Crank trigger was replaced by dealer late April '01 (would die after 15 minutes of driving, let it sit 15 minutes, would start & run for another 15 minutes then die, etc. Their diagnostics said intermittent signal - makes sense, circuit opens when hot, closes when cool). Ran fine until 4 weeks ago.
Cold start is the ONLY time it gives us a lick of trouble.
I had a hard time swallowing the ethanol part, too. I've been using it since '82 (was in Germany before that).
The plugs are platinums (I'm 1500 miles from home right now, the brand escapes me, but I know it wasn't Bosch - I'm thinking Autolite or AC - probably Autolite). Plugs removed were AC, I don't remember type.
It is indeed a California car (was a rental for the first 6000 miles, I bought it from the second owners 18 months ago with 104k. They babied it).
Time to break down and get that fuel pressure gage...

 

I am curious of what the coolant temp sensor and air charge temp sensor readings are... could you access those with the scanner for me/us??? preferably after it has sat (the usual time the condition presents itself and another after it has sat for a few hours after running...

thanx

zroc

 

The two are within a couple of degrees of each other before starting is attempted, typically a few degrees above ambient.

 

heres that tsb

Make: PONTIAC Model: BONNEVILLE Year: 1990

Service Bulletin Number: 90614 Bulletin Sequence Number: 102 Date of Bulletin: 12/89

NHTSA Item Number: SB010956
Component: ELECTRICAL SYSTEM:IGNITION:ELECTRONIC CONTROL UNIT
Summary:
SOME 1989 THROUGH EARLY 1990 BONNEVILLES EQUIPPED W/3800 ENGINE, MAY EXHIBIT CON DITION OF COLD ENGINE LONG CRANK, BUT IF IGNITION KEY CYCLED, ENGINE WILL START- IF CONDITION EXPERIENCED WITH GOOD FUEL PRESSURE & BASIC ENGINE, CONTROLS & SYST EMS ARE PERFORMING PROPERLY, IT MAY NECESSARY TO INSTALL NEW SERVICE MEM-CAL W/R ECALIBRATED FUEL MULTIPLIER RATIO DURING CRANKING-ALL PONTIAC SERVICE MANAGERS


zroc

 

there be more bulletins bout dat bonnie, need to know bcc on prom-broadcast code that is. check spark quality with tester put in a set of plugs. dis ignitions-of this variety-"waste spark" you can call it, with paired plugs on a single coil wether its a single coil or 3 coils in a one piece mold have a tendancy to be thrown for a loop if one plug of the pair is misfiring, it directly affects the plug it is paired with. 3 bad plugs could (if anybodys luck is like mine) cause problems with the other 3. so if my math is correct thats all six giving you trouble and that sux. also are you experiencing any erratic tcc shudder, weird lockup, chuggle? are you able to access a scan tool? is it showing park or neutral when the selector is in either range? if equipped with a in dash tach-does the needle show any movement while cranking? same question applies to scantool readings. rpm signal?