I live in Stockholm Sweden and I’ve have a 1995 Bonne SSE 3.8L (13500 miles). The car is an import from Dallas and I’ve owned it for many years now.

A few weeks ago the weather got really hot in Swedish terms (30 degrees celcius). Then the car began to suffer from increasing engine problem over a few days. In the end I barley manage to drive to the repair shop. But since the 95 is a really rare model here, they seem to be a bit lost with this problem. Now I would really appreciate some input what the problem could be. The shop has done some research on come to the following findings:

DESCRIPTION
When the engine is cold we can start it. Engine then runs okej on idle. We press the accelerometer pedal, and the engine starts to behave strange. It seems to miss on the ignition on some cylinders. When the engine gets warmer we can’t start it any more. We have to wait for an hour or so to get it running again.

The mechanic thought it was an ignition problem. He found out that there were no sparks on one side of the engine when hot. Since the 3 coils seem to be cross-connected, driving spark plugs on both sides on the engine, he figured that it must be the ignition module. We change to a new module, but the fault persists. They also tried to make a better ground on the battery, but with no effect. They disconnected the o2 sensor, but it has no effect on the problem.

We also thought it could be a fuel pump problem, but then the engine wouldn’t run when idling, would it? They have tried start gas, but with no effect on the behaviour.

What can you experts say about this? What should be our next step?

Best regards,
Sebastian Vidovic

Did the car overheat as well?

A badly plugged fuel filter will make your motor run horrible.
How does your fuel pump sound when you 'key up' the ignition?
Does it sound slow and sluggish or does it 'prime up' right away?
A bad fuel pump will only run the motor until the pump over heats and shuts itself down. And will not work again until it has cooled down.


This was a good attempt at finding the problem

This will not bring any good results to the motor running any better.

Again a bad fuel pump will at best run while it is cool. But quit working when it is hot. Also will mimic a bad misfire when its cutting out.



At a quick glance at what your going through....about the only thing I can suggest is look through our 'Tech Info' section . Found Here Look into the area on the sensors and how they can be diagnosed for faults.

Sensors of interest would be your....MAF....MAP...TPS....IAT

When is the last time you replaced the fuel filter?

Thank you for such a fast an detailed answer! It’* very much appreciated.

No, the engine did not overheat according to the dashboard thermometer. But when cranking the motor in desperation I smelled overheated electrical components. If it’* related or not, I don’t know. Hopefully it wasn’t the coils I smelled…

I haven’t checked what the fuel pump sounds like, but I’m getting more suspicious about it. My problems seems to be similar to the guy’* in this thread : https://www.gmforum.com/t281756/
He ended up happy when replacing the fuel pump after digging deep in the ignition area.

Also, we have the misfiring symptom (which confuses my mechanic) that you relate to the fuel pump. And the thing that it works slightly better (on ideling and just above) when its colder outside and the engine is cool.

The mechanic have probably checked the fuel filter already, but I’ll remind him when I’m forwarding your much appreciated feedback. It was replaced some 1.5 years ago.

This might seem like a dumb question, but were is the fuel pump located? In the engine compartment or near the fuel tank? When I floor the accelerator I noticed some kind of choking sound from the air filter area. But the air filter seems to be all right. Could that be the fuel pump struggling?

My father who owned the car before me claims that it could be the ignition wires that runs from the coils to the spark plugs. He says that these must be replaced on a regular basis (once a year or so) since the conducting material is coal and sensitive to wear and tear. Is that really true? Cause this I’ve neglected. Still I find it somewhat hard to relate to the severe behavior of the engine.

Very best regards,
Sebastian

The ONLY dumb question, is the one you DONT ask! The pump is located INSIDE the fuel tank. To get to it the tank has to be dropped on that year model, along with the exhaust (exhaust pipe goes under the passenger side of the tank and gets in the way)

Yes it COULD be the plug wire, they need to be changed periodically... not like oil... but periodically. You might look into that &/or the plugs themselves... I had a similar problem with my 94 and it turned out it was 2 fractured plugs, to the naked eye they looked ok, but my mechanic noticed a hairline split at the base of the ceramic insulation and replaced both and problem solved. Not to say that this is your problem but its worth looking into... plugs fracture easy when not installed properly, and do wear out over time so theres 2 options for a fix

good luck
- TL

Okay, here’* an update. We’ve replaced following parts:
- Ignition module
- Ignition coils
- Ignition wires
- Sparkplugs
- Fuel filter

The engine runs better, but still stalls on 3.500 rpm with some misfires. Now even the mechanic suspects the fuel pump to be somewhat faulty. So we want to replace it, but there’* none in stock here in Sweden.

I figured I could order it on-line and get it shipped with FedEx. I want to order the right part on first attempt. Any recommendations where to order? Maybe you even got the gm-part number that seems necessary in to order from gmpartsdirect.com?

GM Parts Direct: Your direct source for Genuine GM Parts
Description Year MSRP Your Price
PUMP ASM, 95-99 $215.30 $111.96

GMPartsDirect.com - Find a Item


Parts.com
Description Year Dealer Price Your Price
W/o supercharger 95-99 $215.30 N/A $123.80

1995 Pontiac Bonneville W/o supercharger - Parts.com


Best regards,
Sebastian

Finally, my sweet heart is okay. It was the fuel pump the whole time.

Yes!

Congrats

Todd

good job

congrats on getting her back on her feet

it can be a pain sometimes but its all worth it in the end